Any questions on the wonderful rifles known as Rifle Mosin, (in Russia), and the Mosin Nagant here, can be answered here -
http://www.russian-mosin-nagant.com/ the best place I have found for Mosin info. Yes, the 1942r barrel shank stamp on your M38 indicates what year it was built. The "r" stands for the Russian word "god", which means year. Look for the arsenal stamp, too, and see the history come alive as you explore just all the markings on your rifle.
My first M38 was a gift, and it started me on a journey of exploring the strange and fun world of collecting the surplus rifles that sometime in the future, just like the Mauser and Springfields after WWII, will be long gone.
But, for right now, you can collect the whole set cheap! And, since the round is still in miltary production, surplus ammo will be available for quite a while, too! Longest serving military cartridge, ever. Nifty.
I would love an M39, but can't afford one, yet. Have M38, 91/30,(still paying on, I am that broke), and another 91/30 on the way.