Here´s an interesting thread on original omega crowns modified to fit vintage speedies. They´re original crowns made for another reference, but with a similar look to the vintage ones. If you wan´t to change the modern one, and can´t find a NOS, I´d consider this option: http://omegaforums.net/threads/speedmaster-crowns.7964/
Yours is a replacement. No big deal. Richard is quite the Speedy maven. But I have to express what I have noticed about the 145.012-67 crowns. Most of the '67's I see have a different crown than the one he shows which was used on Speedmasters preceding the 67. I believe the 32 (might be off 1 or 2 teeth) tooth crown is correct for '67. Or maybe even both are correct. Here's some of the reasons I came to that conclusion. This is not conclusive evidence of course, just my observations. Would love to hear more opinions. Here's one of Gianvittorio's (LONG time Italian Speedmaster Collector) '67. Here's a 145.012 instructional showing same crown whereas the 105.012 instructional shows the earlier crown, and a different diameter (105.012 is on bottom) Here's one that was said to be in NOS condition bought from the original owner. http://www.corrvintagewatches.com/detail.php?productId=149#
In the Master of Omega, there was a change from 7 mM crown to 6.5 mM crown beginning with the 145.012 and 145.022 as you have pointed out. So that may be an original crown and my assessment incorrect. The crown has a gasket and is routinely replaced when the watch is serviced. I don't place much importance on having an original one. The same is true for pushers and crystals. I want my watches to pass the pressure test so that they can be worn. If I like a watch and it has an original crown, that's nice because it's original. If it's been replaced, that's nice because it shows that the watch was taken care of. If only the rest of my life was so satisfying. LOL