Dating:
The pic on the shirt is from Elvis' 1968 comeback special (see pic below), so it's definitely not from before then. Re: dating I agree with the above posts, you'll see a marked change in elvis prints towards the end of the 70s.
Desirability/Price:
This is the kind of print that I regularly hunt for on ebay. On ebay now, the only comparable piece is offered by Vintage Retro Wear for about $72, but he's had it up for almost a year and who knows how much it'll actually sell for. I'd say put it up at full price, Elvis tees don't do well at auction.
Side note: I'm going to watch my copy of the comeback special again to see if anyone is wearing a similar tee. However, I don't think that there were any concert/promo tees officially made for the event.
I'm interested, email me and we can do a trade/sale.
![Image](http://4.bp.blogspot.com/_NTKDCVTB2aQ/S_mqCOpk2FI/AAAAAAAAABE/Iis6nBZSWWI/s1600/069_3726elvis-presley-posters1.jpg)