Patterned steel is patterned because of the mix of irons/steels
look for thick walls and as little pitting as you can find. unless they have already been cleaned up, it would be very unusual to not find some pitting or frosting in the bores, barrels should ring if hung by the barrel hook and lightly tapped (no metal - i flick my finger nail on them)
the patterns are in the barrels - and is determined but the constructions- twist is a candy cane sort of look - damascus is a swirl and there are variations in each
if you are new to it, it may be best to have them checked by an expert
take a look here for some great examples
http://parkerguns.org/forums/showthread.php?t=12067
search the hammer guns threads for damascus or twist and you will find lots of pictures
Threaded Mode