An Unusual Mentmore Diploma


I think this one takes the biscuit for rarity and mystery.  In most respects it’s a perfectly ordinary Mentmore Diploma.  What makes it stand out from the crowd is its translucent barrel.

The explanation for this that comes first to mind is that it’s a demonstrator.  There are a couple of problems with that, though.  So far as I am aware, British manufacturers just didn’t do demonstrators in the 30s and 40s.  We are used to ink-in-the-barrel demonstrators nowadays, and the idea of a clear barrel to demonstrate the operation of a button filler seems rather strange.  It’s not impossible, though.  We can’t discount the possibility.
Could it be, perhaps, a trial of a new and experimental celluloid?  Others, like De La Rue, had developed semitransparent plastics.  Mentmore was never afraid to try something new and perhaps this was a prototype that never went into production.

Finally, this may just be a freak celluloid that lost its colour and became transparent.  This is the least likely explanation.  One would expect there to be a batch of tens if not hundreds of similar pens, and they just don’t seem to exist.  In my many years of fascination with pens, this is the one and only example that I have seen.
Whatever the explanation may be, it makes an interesting pen.  Fitted with a translucent plastic sac as this one is, the amount of ink available is visible.  Also, you can see the action of the pressure bar as the button is depressed.  That’s not something you see every day!


17 thoughts on “An Unusual Mentmore Diploma

  1. Fascinating; and a splendid subject for speculation. With a clear sac it would be interesting indeed – and a useful reminder that a good flushing was required from time to time.

    When one reflects on the large number of manufacturers at that time, and given the essential simplicity of fountain pens generally,perhaps the pen makers were willing to try very hard to come up with some sort of unique selling proposition.

    Most of them opted to produce wonderful colours and patterns and decorative features, whilst so many buyers bought plain black pens!

    1. As I said, that’s one explanation. The interesting part though, if that is the case, is what the mechanism was for the barrel becoming transparent and why it affects this one pen and no others that I’ve ever seen? As regards the cap, there is no reason to think that’s a substitute. Such pattern as there is on the barrel matches the cap.

      Tell me, why do you start a sentence with “so”? It’s grammatically wrong and it doesn’t add any meaning to what follows it.

      1. I touch-type in real time as if I’m speaking out loud – the So… is a thoughtful pause, eyes rolling upwards; hand holds chin. Or Imagine the use in quoted narrative.

        I’m sorry if it bothers you.


      2. I confess to being a grammar Nazi when it suits me, but no, David, it doesn’t really bother me. I find your explanation interesting though. The “so” reflects that moment of thought before you begin to write. Isn’t that a bit like showing your working in the maths exam?

  2. Valentine did similar pens in green marble with the cap not being transparent as did Kingswood. The only difference is that the Valentines are lever fillers. As I have seen a handful of such pens now, my supposition is that this was a deliberate finish and not that the barrel has lost colour (although I think I have seen this happen, but only in patches, not the whole piece) and the caps are always opaque.

    On the “So…” thing, listen to the radio or watch the TV – people do it all the time now in speech and I find myself doing it sometimes. It seems to be like creeping into the language like.


    1. That’s very interesting, Simon. I think Conway Stewart did a similar thing. I’m still wondering why, if this transparent barrel was a deliberately produced Mentmore product, this is the only example around.

      So I see what you’re saying, like, about these modern linguistic fashions, innit.

  3. I tend to go with Simon, it was a fashion response (principally) to the Vacumatics and the originally clear barrel has discoloured over time.

    I have a horrible feeling that I bought one of those CS 475 pens off you some years ago and thought I had been conned until I found a picture of a transparent barrelled pen on the Conway site and saw that not only were the barrel and cap different colours but that the patterns are slightly different too.

    Like your Diploma the 475 would originally have had a rubber sac, so there was no real benefit to a transparent barrel other than fashion. It was probably the gasses given off by the sac that discoloured your barrel.

    Am I able to post photos on your site? I have a couple that you may find interesting (if I can down load them from my phone (technophobe!)).

    1. If I understand you correctly, you think that the barrel began clear and arrived at its present state through the same process as that which blackens Jade pens. I have a bit of difficulty with that one. While it is perfectly possible that the barrel began life with the transparent parts clear and subsequently ambered, I hardly think that the process would create little patches of the same pattern as appears on the cap. Also, if it was a result of the outgassing of chemicals from the sac – a process we are familiar with and see often – why aren’t there are many more Mentmore Diplomas in the same condition?

      There is an “IMG” command in the reply box which should enable you to attach an image, though I confess I’ve never used it myself.

  4. It seems we have reached the allowable depth of comments and replies in a single comment post. Hence, I respond anew:

    “…like showing your working in the maths exam?”

    Quite, (there I go again with my predilection for paltry precedence; Entschuldigungen Mein Führer) – I am a classically trained yet still practicing Electrical Engineer. My (wonderful) life is very much like a never-ending Math(s) exam.

    So (sic?), in my original post the “So,…” is indeed Ponder; unlike the matter-of-fact “So,…” as in (e.g,) Byron’s “So, we’ll go no more a-roving”.

    1. Excellent points, well put. However, I would suggest to you that Byron’s “so” is the lead-in to the conclusion of his argument which for poetical purposes he reverses, rather than the pondering “so”. If we were to rearrange the poem to reflect the usual train of thought, it would run

      Though the night was made for loving,
      And the day returns too soon,
      Yet we’ll go no more a roving
      By the light of the moon.

      For the sword outwears its sheath,
      And the soul wears out the breast,
      And the heart must pause to breathe,
      And love itself have rest.

      So, we’ll go no more a roving
      So late into the night,
      Though the heart be still as loving,
      And the moon be still as bright.

      That’s how the logic runs, and though Byron may have been “mad, bad and dangerous to know” he was eminently logical. However, as the great poet that he was he knew that there was greater effect in surprising the reader with his conclusion before stating his argument.In fact, it works in the same way as your final “So” above.

  5. Apologies for breaking the moment but…… I too have a similar Mentmore (albeit Supreme) with black marbling over a clearly transparent and unstained barrel. The cap is all black, the GF clip (and fill lever) un’M’onogrammed and in a sort of ‘pelikan-esque’ style. Although I would have imagined the cap to be foreign it does fit perfectly and the material and the top of it matches the style of the black lower barrel ‘jewel’. Going on your above conversations it may be, possibly, perhaps, genuine?

    1. It may be genuine. Particularly during World War II, pens were sometimes turned out with mismatched caps and yours may be one of those. Yours is the third transparent barrel I’ve heard of now, that is, mine, yours and one that my friend Widget owns. Seems to have been a Mentmore thing.

  6. Hi Deb I have discovered that I also have a Mentmore Supreme with transparent barrel. Mine is a lever filler in beautiful burgundy marble with black veins.

    The cap and barrel match virtually perfectly apart from the cap being solid and the barrel transparent. Have little doubt that this is exactly how it was manufactured. Would post a picture of it on here if I knew how to.

    It should be on the Penworkshop website in the next few days.



  7. Just a quick note to add to this thread. I also have a Mentmore with a transparent barrel but to add to the confusion have just bought a Savoy pen which has the same feature. It is in marbled green with an opaque cap but a transparent barrel. Could the Savoy have a link to Mentmore?

    1. In the two years since I wrote that article several more transparent Mentmores have been reported. A Savoy with a transparent barrel hasn’t been mentioned before, which makes it interesting. For several years there has been debate about who manufactured the Savoy. Several manufacturer’s names have been put forward. No one until now has suggested that it might be made by Mentmore. To be frank, I still believe, on grounds of the way the parts are manufactured, that it was made by Langs.

      Manufacturers often shared batches of celluloid. It may be that this is the explanation for the transparent Savoy.

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