I discovered an estate sale today by accident. It was mid-day and it had been picked over, but I checked it out. I saw an old, beat-up cross pein hammer, and thought that it was cheap enough ($5.00) to be a user. It's about 2 pounds, so it would be good for light forming.
I saw that it had letters stamped in the head, on top, bottom, and both sides. The letters ended in RR, so I thought it might have come from a railroad. After I got it home, I read C&STLRR, with the T having a gap in the vertical line. The T with the S in front of it probably meant St., so I was thinking C&St.L RR. Research didn't show up any viable matches, and I looked it over again. On the top I could make out a faint P in front of the C, making it PC&STLRR. This matches the Pittsburgh, Cincinnati, and St. Louis Railway, which is first mentioned in the late 1860's and merged with the Pittsburgh, Cincinnati, Chicago, and St. Louis Railway in 1890.
That makes this hammer pretty old, and I believe it earned it's bumps and bruises. Notice the 1/2 pound of nails substituting for a wedge in the head end of the handle!
By the way, in some photos the head looks polished around the lettering. It isn't, I scraped the dirt and rust out of the letters, and used a quick wipe of oil to make the letters stand out.