whats with this "C1" on my alternator?

[weider1717]

Hey guys! question..you see that "C1" on my alternator well it was on there before I bead blasted it so after blasting i had to take a marker and write it back on there looked a bit more stamped before hand.

any idea what it means and that is factory correct? my truck I bought it from the 2nd owner who had it since 1989 with 29k miles on it and i bought it in 2007 with 63k miles according to him nothing had ever been touched including the water pump etc so I assume it came like this.

wanting to make sure because i just took it back off and REALLY went through it and make it more factory fresh with a fresh tumble in media so I want to put it back if its spposed to be there or not if its not. thanks!