Colt Bolt Question

[Submariner]

SAW lists the following part:

SP61538 BOLT, STRIPPED (MPC or C)

I was taught that all Colt bolts are marked "MPC". Then I came across a "C" marked bolt when changing extractor springs. It didn't have the "MPC" but I knew it was bought from a reliable vendor as Colt.

Is there any difference between the two bolts other than the lack of "MP"?

[Robb Jensen]

I've seen them marked either way.