Thank you all for the replies, especially Big Lou with the dates. I still have not procured that reference book with the dates but want to pick up one if I can find it.

Overall, I am really happy I got these twins and looking forward to visiting the range soon to test accuracy.

I am thinking of moving those nice grips to the model 28 since the 28 is in better overall condition but not sure if those grips would be appropriate for the m28 in the 1967-68 timeframe.