When you say you think it is somewhat rare/valuable, do you mean you think it is a rare/valuable variation of a Luger or just that Luger's are rare/valuable as a breed? I make no claim to being a Luger expert, but DWM is one of the more common makers and this looks like a typical post-WWI pistol that used reworked and/or new parts. Not saying it isn't a nice collectible pistol, just nothing jumps out to me as being particularly rare. Google Jan Still Luger pistol forums, you can find a wealth of knowledge there.
I was just curious on valuation, from the research I've done it seems that fewer guns were produced in 1921 than 1920. In trying to find out if it's worth reselling and making a profit or if a "shooter" quality/rarity firearm.