Maybe the case was polished a little too enthusiasticly and lost a mm in diameter?
I compared it to this one: here
Looks like the same case to me, but there's no overhang.
You might be on to something here.
Was there an OPS dial without the "automatic" under Enicar as seen here?
That's a dial variant I haven't seen before as far as I remember.
I found some information over here
Seems to be a very specific crystal because as it says there crystal’s inside shape is made to hold the tachymeter scale.
In the Brochures & Manuals section of Enicar101.com there's a 1960's Guide manual showing an Anchorage bezel.
And a 1970's one showing a cushion case Guide with the Gambier bezel.
Interesting and confusing subject.