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My guess is Engelhard was in the middle changing the variation. "A soft transition" in between both series. While they were in the middle of the transition the serial number stamps were erratic and not in proper order. Back then it was all manual labor. Which is what makes this stuff so interesting! @themanwithnoname

Yeah, each of the pieces is unique, so you're getting something that's special. It's not like the standard bars you get now that all look and feel basically the same. You're buying something that has its own personality. That's cool!