I just acquired what I think is an H&G mold, but the maker is not marked on the blocks or sprue plate anywhere I can see. It is a 6 cavity iron mold, stamped "73" on one block. The cavities match other pictures I've seen of H&G #73 molds, but without a maker's stamp, I'm wondering if other companies also made these (Ideal maybe?) or is this maybe a very early H&G mold?
The handles are the type with the pivot at the far end of the blocks. The sprue plate has a flute or groove between the holes, like other H&G sprue plates, but it's flat on top, without the slight ridge around the groove that I've seen in other pictures.
A final question is about cleanup. I'm tempted to clean the blocks in my ultrasonic cleaner to get the old gunk out. I know that would remove any bluing left on the blocks though, so I'd have to re-blue them (just cold blue). Not knowing anything about the value of this mold, though, I'd hate to find out I ruined the value of it, as I'll probably sell it once I finish casting from it. (I don't own a .38, and don't have much need for this one.)
Thoughts?