Actually it looks like corwin is already sold out of their Enfields. But you can't go wrong with a good No1 mk3 or No4 mk1. Long branch is always desirable because they're Canadian and supposedly are of a higher quality. Enfields can be anywhere from $150 for a sporterized model with the stock/barrel cut down and the receiver drilled for a scope, to $1500+ for a 50's era Irish contract No4 still in its original wrapping. Most original rifles tend to hover somewhere around $700-800. Or you could do what I did and spend thousands on a No4 T sniper rifle or L42.
If you're looking for a collectors piece, matching numbers is always a good thing. That's the receiver(on the wrist), bolt, magazine, etc.
If you want a good shooter, there's lots more factors. Bore and Crown condition being obvious. Also headspace...Enfields have interchangeable bolt heads numbered 0 through 4 which are installed as needed to maintain proper headspace. 0 being new and 4 being probably nearing the end of its barrel life. There should be upward pressure at the muzzle on the No4, and ideally no cracking at the back of the forestock behind the trigger area. The rifles should have a distinct 2 stage trigger pull (if they don't, someone has committed shenanigans). There's a lot more information, since Enfields were produced in so many variations all over the world, but I hope this helps a little