Hi Henry, hopefully you'll be looking in on this site again soon. Here's one for you as I know that you are a specialist. I already know a fair amount about this coin:
GERMAN STATES HESSE-DARMSTADT 10 Gold Mark
Ludwig IV Grosgherzog von Hessen 1878
Weight: 3.98g and 90% gold
Mintage: 132,000
What I have no real idea about is the grade of the coin. The Obverse is in good crisp condition, but there is quite a bit of wear to the crown and coat of arms.
How would you grade it? Apologies for the photos, I have more high definition ones, but too large to upload here.