A cursory search of the internet suggest that there were date ranges that saw the model 929 made in 2 different versions. The first was from 1957-1973 and the second from 1974-1986.

According to a date code chart, the ‘AR’ serial prefix should put your particular 929 in the second iteration, being manufactured in 1977. This of course is just what I was able to find, and in no way is a guarantee.

If you have a good, reputable gun dealer near you, such as a mom and pop type store, not a big box like Walmart, you may consider taking it in to them to see if they can verify this, as I do not own a copy of the firearm Blue Book.

If I should happen to find myself out at my friend’s store next week, I’ll ask him if he can look into it for you. He just might now the answer without consulting his Blue Book, dude is like an encyclopedia with legs.