It's conceivable that the numeral Ɔ and letters it combines with are a mediaeval conceit rather than truly Roman — hopefully this is still on topic. I'm trying to decipher the publication date of a book published in Antwerp which is written as
CIƆ. ICƆ. XVII.
The last part is fairly obviously 17, and as it's a printed book it could even be 1517, since etching and moveable type had been invented. The peculiar character combinations bear a superficial similarity to M and D: is that what they represent?
The book is riddled with misprints, which would also point to a fairly early date for moveable type. If IƆ is supposed to be D, it would be reasonable for ICƆ to be a misprint, but the presence of C in that group is another point of confusion.
There is a related question, but that doesn't really explain CIƆ and certainly not ICƆ.