I'm trying to positively identify this Lyman Maxi Ball mould which is simply marked "Lyman 50 Cal".
It certainly looks like a #504617, so I'm wondering if perhaps Lyman at some point stamped their #504617 mould in this manner?
I haven't had the chance to drop any bullets from it but using a micrometer it appears that it would drop a bullet of about .504-.505 diameter and about .900" long.