I got a lot of good advice about just using a replacement bow saw blade. Either that or using a bandsaw blade and cutting to length. (Bonus points on that last one for being super adaptive!) Since I’m kinda’ digging the idea of restoring this saw I did some checking myself. Here are some more details.
#1: It’s a bucksaw. When I search on DuckDuckGo “bucksaw” turns up a zillion photos of exactly what I have. (You’re not searching on Google are you? You gotta’ watch out for Google. They’re evil motherfuckers… I’m just sayin.) Lots of people use bowsaw and bucksaw interchangeably but for my purposes if it’s old and wood and looks like a pioneer would use it, then it’s a bucksaw. If it’s not old, not wood, and a pioneer would throw his heavy bucksaw in a lake as soon as he got his hands on this lighter modern device, it’s a bowsaw.
#2: It’s way thicker than a bowsaw. I’m talking here of thickness of the blade, not merely length.
#3 I estimate it’s 1 7/8″ thick. A regular bowsaw is a lot thinner. Though I suppose there’s no reason the thinner bowsaw blade won’t work as well as the thicker bucksaw blade. The only thing doing work are the teeth. The only drawback is that it won’t look right. 
#4 Lengthwise I estimate it’s 29 1/4″ from “pin to pin”. I still haven’t figured out how to remove and replace those pins. On the one hand I don’t want to totally trash the cool old saw. On the other hand I want a working object and not a wall hanger. If I wind up with wingnuts and a bolt I’ll just have to face what I’ve done. (I’m no wimp about messing with old stuff so long as it’s cheap. Don’t ask what I’ve done to some old Mosin Nagants.)
#5 I’m not sure but I don’t think bandsaw blades will do. The bucksaw has cutter teeth and rakers. The bandsaw has no rakers. I think for human powered cutting, I need rakers to get the sawdust out of the kerf. (Also, either the photo sucks of my bandsaw totally needs a new blade too.)
#6 I’m starting to decode the cutter teeth count. My old bucksaw has 2 cutter teeth between each raker. My modern (cheapo) bowsaw has 4 cutter teeth between rakers. This bowsaw blade is $11 and 4 cutters per raker. It says it’s for green wood:
Thus I suspect 2 cutters/raker is for dry and 4 cutters/raker is for green.
