They were no different than any other same vintage 340 pan. The only number I've seen on confirmed originals were stamped with a large "294" in the bottom sump. I've seen similar vintage pans that looked identical but had 394 stamped into the same area, also likely correct but I haven't seen an unmolested original to confirm it. There are a lot of small block pans made that are the same shape and size, both new and used, but the style with the stamped in 294/394 numbers are not reproduced, used market only.