A recent post by another member got me thinking about how to look at an older saw and know whether it is a good one or not. Old Disstons are awesome, but unfortunately the company lingered on into the period where they made some stuff that was not so great, so the name alone does not necessarily indicate you are getting quality.
Obviously you can buy a new saw, or buy from one of the folks who do a nice job fixing them up. That can be pretty expensive though, and it can be a lot of fun looking for "old gold" and then learning to clean it up and sharpen it. If you are looking on ebay it can be particularly hard to tell if what you are looking at (often with a minimal description) is a bargain or a dud.
I thought I would post a few photos of saws I have, and some of the features that in my experience indicate you may be looking at something pretty decent. Here are my thoughts, based on some hits and a few misses over the years. Some of the details you may not be able to see on an ebay listing, but I hear folks often find saws at garage sales and flea markets (not me, the only saws I ever see at garage sales are pruning saws).
In addition to some of the features I mention below, you obviously want to look for damage, extreme rust, broken handles, missing nuts, kinked or bent blade, ridiculously bad tooth line, etc. I am not an expert, your mileage may vary, others may have different opinions (some of them may even be right!), etc. etc.
Here is my favorite rip saw. It is a warranted superior which are sometimes very nice saws. It was an ebay "hit." It was originally a cross-cut saw, and I refiled it to a rip profile. It has about 5 or so TPI. Indicators of quality on this one include the skew back and a reasonably decent handle. I don't see how the skew makes a difference in performance, but I have noticed the lower quality saws (later Disstons for example) are just straight, blocky things that look like they were made as cheaply as possible, and the handles are similarly blocky, looking like they were simply cut out with a jigsaw. This handle is certainly not some sort of premium product, but the edges are eased, and it looks like you could comfortably hold it for an extended period of time.
IMG_0121.JPG
In addition, it has a nice etch. I could not see an etch in the ebay listing for this one, but if it isn't too crudded up you can sometimes make them out if you are buying in person. I don't know who the Willard Saw Company is, but the fact that they wanted their name on the saw indicates to me that they did not think it was complete junk.
IMG_0119.JPG
This is another warranted superior. The indicator it may be decent quality here is the little cut-out at the toe. Makes no difference in cutting, but again, it is a little something extra the manufacturer did that seems to go away as the quality began to decline. It also has a nice handle, with all of the sharp edges eased, and another nice etch, this time from the "Simmons" hardware company in Boston. This one was in pretty rough shape, and the etch was not visible at all until I cleaned it up. It turned out to be a really nice, taper-ground saw.
IMG_0124.JPG
IMG_0123.JPG
IMG_0126.JPG
I have a couple of "name brand" saws for comparison, but I guess you can only do a certain number of pictures in a post, so I am going to post the "no-name" ones here and will do the others as a reply.