The AY code on your 700 is more than likely the barrel code for date of manufacture. The first letter is the month and second is the year. If I did my conversion right your rifle was made in March 1974. The model 700 didnt come out until 1964 I believe so the first Y in the series wouldn't make since for your rifle. For more info on how to use the codes check out this link
http://www.rimfirecentral.com/forums...ead.php?t=9555