I have seen some m39 with 1970's dates on them? Did they actually make them in the 70's? Which ones are more desirable? I would assume the ones from the 70's would be in better shape but worth less.
No. The opposite. The 1970's late dated ones are actually rarer, and bring a premium.
They are very unique, and were either made in the 70's or earlier and stamped such in the 70's, but not very much is known.
Read more about them here:
http://www.mosinnagant.net/finland/finnish_mosin_nagantm39.asp
There is info to suggest that "these 1967-1970,1973 dated rifles were used primarily for marksmanship training of officers."
M39's are very collectible, many variations exist.
In Canada, M39's are quite scarce, much more so than in the USA. They are climbing in price in both Canada and the USA thanks to supply and demand, as well as more people finding out what they are.
Some people say they are basically a Mosin, but once you see and handle one, they are a different firearm completely, in a class of their own.
Not to mention they are packed full of history.
Here is a page with rarity numbers of mosins on a scale of 1-10. Scroll down to the M39's and other Finn variations. Note that this list is a little outdated, and there have been some changes with production numbers etc coming to light, and hence changing the rarity up or down for many rifles, but it will work as a very basic guide.
http://7.62x54r.net/MosinID/MosinRarity.htm
A "late date" is a 7/10 rarity, while a normal M39 1944 Sako is a 4/10.
Adjust the price accordingly.
Hope this post answers your question about the late date ones.