What does the "Roman" numeral Ɔ represent?

Question

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.

Answer 1

The most likely reading (which seems consistent with the look of the piece of the book shown and the dates found for other books published by Caspar Beller by a quick Google search) is that the C is misplaced into the "ICƆ" group, i.e. the corrected reading would be CIƆ IƆ C XVII, i.e. MDCXVII = 1617.

Answer 2

It reminds me of this statement I read on wikipedia once.

The early Roman numerals for 1, 10, and 100 were the Etruscan ones: "I", "X", and "Ж". The symbols for 5 and 50 changed from Ʌ and "𐌣" to V and ↆ at some point. The latter had flattened to ⊥ (an inverted T) by the time of Augustus, and soon afterwards became identified with the graphically similar letter L.[49]

The symbol for 100 was written variously as >I< or ƆIC, was then abbreviated to Ɔ or C, with C (which matched a Latin letter) finally winning out. It may have helped that C is the initial of centum, Latin for "hundred".

https://en.wikipedia.org/wiki/Roman_numerals#Origin_of_the_system

That doesn't exactly answer the question, especially since your example is from the 16th century, but maybe this has something to do with it.