I recently came across a Vulcain cricket that had no sound holes on the back, the case was stamped proper.
I have done some research on ebay, google etc.. cannot find examples of the no hole case back (the case back has the proper alarm pin so im sure its original back). I suspect that it may have been the waterproof version? (but does not say waterproof on the dial or caseback).
there was another thread on watchuseek on 2014 but no definitive answer there (the link to the answer was broken)
Does anyone have any information on this? I have attached 3 photos of the watch.