Without apology I am not a Colt man. However I do apologize for not reading Wikipedia before posting. According to them:

Irrifleman is correct. There was no Colt MK II. The Colt MK III with sintered metal internal parts was introduced in 1969. It was discontinued in 1983. The Colt MK V replaced the MK III. MK V had cast internal parts.

So ... both Irrifelman and his gunsmith were correct.

I remembered the 8" MK III that I bought new about 1981 had sintered metal parts. I did the best trigger job on it that I could but compared to S&Ws its trigger pulls it still stunk. Stoning the internals did not cause any problems in the short time I owned it.

Your not understanding that it is not explains your post. Not to worry. I get corrected all the time and am better for it.