Hi Pete, maybe i was i bit "liberal" with my reply, it`s not common at all for this period. After the M1/ prefixing system was "well in use" by all, say around early 1936 when these most certainly date from, (going on the style of the numbers according to my research on this maker and period) only a few types of attachments were used by all licensed makers for the small badges. (excluding Austrian makers but including Sudetenland makers) (Official badges, not just general small badges) and these were certainly not one of them, I have seen it before, and like i said, this specific attachment is "known" from M1/77, but i too, have only ever seen this once - on Parteiabzeichen. HJ badges i would not know because i dont collect them.
Probably a one off in order to cover orders at one specific time when they (or the sub-contractor) had no more proper attachments, or standart attachments.