I bought two Rudy Muck mouthpieces off ebay recently.  One was a modern 17C and the other and older model marked 1C7 .  I was curious if this was a misprint or a different model so I did some measuring.

It appears that a moderm 17C has a Cup Diameter of 15.75 mm.  

So I set my caliper at 15.75 and placed it on the cup of the 17C and it fit pretty good.  Seems that this 17C is upto spec's.

Now I measure the older MPC.

Looks like the cup is a bit bigger on the 1c7.  OK, so lets look at some other measureable things.  My caliper is a bit too big to fit in the cup and measure the throat but I eyeballed it and they both look around 3.7mm, too close alike to tell a difference.  There are other things I measured though and found differences.  The thickness of the shank was noticable:

The newer MPC has a thicker shank, what about the inside of the shank?

Interresting, so the older MPC with a smaller shank is larger on the inside.  This would seem to allow more air to flow with less pressure.  Well, there's on other think we can look at that I could measure, the thickness of the rim.

I could visually tell that the rim on the newer mpc was thicker.

So what have we leanred???

Well, a Rudy Muck mpc engraved 1C7 is not the same as a modern 17c.  I've seen other older RM mouthpieces with 17C printed on two lines, perhaps this 1C7 is also one of those and he changed the specifications on his mouthpieces.  When I tried them both out, I had greater range on the older one. It's probably because of the thicker rim of the newer model. As the MPC sat in the same place on my upper lip, there was less upper lip to vibrate.

Disclamer: My measurements are not to be considered those of a professional. I am merely a hobbist trying to determine the difference between these two mouthpieces. The point of the measurements is to compare the differences between them.