The two-letter date code is most likely found on the forward section of the trigger guard.
The Beretta 71 is a fantastic gun, and one of my favorite all-time firearms. First, it's the most reliable .22 pistol I've ever encountered, meaning total reliability with the widest-spectrum of .22 ammo. I have some others that are close, but the several 71's I've shot have the edge.
The grip and natural pointability is also probably the best of any
handgun I've ever encountered -- for my hand anyway. The extremely low bore axis makes aiming feel like you're pointing a finger.
Very nice SA trigger, and the gun is just absurdly accurate for the size -- more than it has any right to be.
To top it off, it's a beautiful design, beautifully made and finished.
There are two main downsides that I see. It has relatively small/primitive sights -- they can achieve satisfying precision, but they are in no way high-vis. And not easy to adjust at the range.
Also, the 8-round mags mean it's a bit lacking in the firepower department (even .22 revolvers typically carry more these days), and spare factory mags are extremely expensive and not easy to find.
You'll probably like this article. Place your bets -- Israeli sky marshals armed w/ Beretta 71's in .22LR vs. AK47-wielding Arab terrorists:
https://www.tactical-life.com/firearms/israeli-mossad-22-lrs/
Edit to add: there's a good amount of reference info to be found here:
https://berettaforum.net/vb/showthread.php?t=95801