I saw a couple of Disston crosscut saws at a local antique mall.  My best guess
after consulting the Disstonian Institute web site is that one is a post-1940 D8
(medallion says “Disston USA”, 4 nuts, skew-back) and one is a post-1940 D7 (3
nuts, straight back).  My big question for the list is how much a bow in the
blade matters? Both saws have a distinct bow when you sight down the blade, one
about 1/8” and one more like 1/4”.  Not a sharp bend or kink, but a definite
bow.  The plates are darkened, but do not look heavily rusted or pitted. Any
other tips on what to look for when considering buying an old saw?

The “otherwise” are two back saws that I own that I’m not really sure where they
came from.  Either my grandfather or my father.  One has no medallion (or it is
missing, there is a hole with a missing nut, was the medallion ever used as a
saw nut?), the blade is etched with “CHAMPION”, “warranted high grade spring
steel”, “A tool of real merit”.  A quick googling does not reveal anything.

The other back saw has a medallion that says “Pennsylvania Saw Corp, York PA”.
Googling reveals that it was in business 1938-1979.

I think that both of the backsaws are 1970 or later.  Is it worth attempting to
sharpen them or should I keep an eye out for older saws?  What makes an older
saw better?  Is it that the steel is better quality so the teeth take  and hold
a better edge?  Something else?

thanks,
andrew