I have written extensively about the Waterman 513 before. The search box above will take you there. It and the 515 are probably the best post-war Watermans. The 1955 W3, while still a good pen, shows a decline in quality.
This striated blue version is very attractive, the gold plated trim fitting well with the pattern. The box lever design is a little different from earlier examples but is still quite robust. The clip shows a little wear but much less than I have seen on many examples.
When I’m researching a pen, I take a look in eBay. I find it quite amusing that among an entire page full of 513s, a couple of sellers describe the pen as rare!
This example is English. Canadian 513s are near-identical. The US Stalwart seems to be the same pen. There is another US pen, the 513J, which has a different clip and tassie and may be earlier. I have seen a variety of nibs in these pens. Some of this may be from the factory using up stock, but others, like this one, have a replacement. This nib is a W3, the later type, and must therefore be a replacement.
With its gold plating and variety of patterns, the 513, like most post-war Watermans, makes a fine collector’s pen. It also makes an excellent writer. Waterman nibs are invariably good, whether flexible or firm and the pen is a decent size and sits well in the hand.