As Andrew Hooper kindly sent it to me I’m taking another look at the NA Safety Clip today and comparing it with the more familiar Swan Metal Pocket. As the N is over the A in the pressing I would say it should be that way round. There is a slight difference in size. The Swan is 119 mm long and the NA 117 mm. The NA weighs 16 g to the Swan’s 15 g. I would think the latter figure is probably not all that significant and it may be within the margin of error of my digital kitchen scale – not the most precise of measuring devices.
The method of manufacture appears to be the same but the design is different. The NA is a very slightly more complicated pressing in that it has a tiny tab above the label to enable pulling the front forward to insert the pen. The finish is different. The Swan holder has an only slightly shiny, almost matte finish whereas the NA appears to be finished with gloss paint.
None of this, of course, takes us any closer to finding out what company had the NA Safety Clip made. Using it as a search term in Google leads to a spring hook for a dog lead… Not that helpful, really! Unless someone comes up with the answer to this puzzle that’s all I have to say on it, except that I would not advise anyone to use these things for the purpose they were originally made for. Almost all of them have deteriorated and have internal rusting which will scratch a hard rubber pen.