A few years ago, maybe 8 or so, I found my first back saw in the wild, in this case a flea sheed on Sjealland, the capital island of denmark. The hanldle has wormholes, the blade and spin were rusty and the tooth line was weavy as the ocean around Sjealland in a big storm. I wouldn't have taken it, but it was the first backsaw. And it wasn't expensive. (Buying second hand in scandinavia is allways cheap.)
Not sure what it was meant to be used as. If it was american I would have said mitre saw, but the blade is thinner than on the mitre saws and the hang is much lower. So I think it was meant as a r e a l tenon saw.
This summer I'm clearing my shop from all tools I don't use, because I will move to a much smaller shop in the near future. So I cut of the weavy tooth line witt the sheer and toothed it with 8 tpi rip. Though I really like it now, I know I won't be using it in the next few years. (No construction work in sight.) So I send it to a good friend to be used what it was meant for.