Welcome to the forum, it is a a bit too hard to judge value with these pictures.
It appears to be in good original shape, but it could have been reblued at one time? Just need better pictures.
could be $600 or $1200
All small parts should have the last two of the serial number, it doesn't look like 123x? I don't think they made that many lugers in 1918. I know you were giving a x as an example and value would not be affected by what suffix it is, but for legal reasons, you will want to state, DWM, 1918, sn 1237 d luger when you sell.
A 1918 should have a wood base, although to the average person they wouldn't know or care.
How is the base of the magazine marked (some folks get all weird about calling them clips
)