What you have is a very nice, if very common, Luger variation.
The byf means it was made by Mauser during WWII. The number "42" means it was manufactured in 1942. I can see that all of the obvious numbers match (excepting the mag) which is good and the blue looks like it is probably original (from what little I can see of it).
I'm not much on the leather stuff but the year is period.
Valued at anywhere from $700 - $1,200? Hard to say for sure...
Congratulations on your first Luger. It's a handful of history.
