Direct Connection Valve Covers

Another time I walked into a junk yard looking for rear drums to a ‘67 Oldsmobile 98. The fella comes walking back with a drum and asks if that’s the one. I’m 18, don’t know Jack! I shrug my shoulders and say it looks good. He asks if I have the original drum with me. I did! I brought him the drum, he takes a 1 second look at it , grabs the drum he brought out and says, “Nope! Wrong drum, I’ll be right back!” He had it! I couldn’t tell you what he saw. But he knew in a near instant.