Unusual Victor XVI Dataplate Suffix

[Zeppy]

I vaguely recall this being discussed at some point in the past couple decades, but don't know if anyone definitively answered the quesiton. I saw this on Facebook marketplace, and the dataplate caught my eye. The D suffix makes sense for the L-door, placing it around 1912, very late in the L-door run (the new cabinet model came in around 60000, so this would have been among the last 300 L-doors). But what the heck is the additional M suffix for?

[Silvertone]

Victrola XVIs in the range of 53535 to 60726 have a different governor and some, if not all, are reportedly stamped "DM" on the dataplate.

If owners with XVIs in this range can verify if their plate is stamped with a DM, we may have a more definitive answer.