My copy is pressed in hard, slightly flexible vinylite (thinner than a shellac record) and has delta numbers in the runouts:
A side runout, etched: A-2082-4 Δ11736
B side runout, etched: Α-2083-4 Δ11738
I don't see a circled MR in the runouts. Was my copy nevertheless pressed by Monarch Record Mfg. Co.? And if yes, is the delta number dating chart at this 45rpm website: https://www.45rpmrecords.com/date_monarch.php relevant for 78rpm pressings too?