Mittenwalder Handarbeit means: Made by hand in the german area of Mittenwald. That is in the very south of Germany, near Austria. BUT there is no name of the maker. So I believe it is just another factory "hand" built bass. The tag looks very fresh for an older bass, maybe even someone did a fake....
If you like the sound and it does not have serious damage, 1500 maybe okay....who cares if it is plywood or solid wood as long as it sounds good to you?
Shop bass? Yes, maybe they think of an very old man with a beard who is sitting in his little shop in the dark German woods.
He builds the basses entirely with his own hands. The wood he uses was stored by his grand-grand father in 1885.
All he needs is a saw, a knive, human bone glue, and a secret laquer made from the blood of an alpha wolf.
He builds one double bass in every year, not knowing that he produces some of the greatest instrument that will be very expensive fifty or hundred fifty years later...and now you have the chance to get one of this rare "German Shop Basses" for 1500 Dollars... ;-)