[lugerholsterrepair]

Germany on the barrel make sense. There should be some marks on the pistol..Other than the serials.
Are there any serial numbers on the ladder sight? 2 digits?

I was told this gun was a war trophy from WW1....Whoever told you this is mistaken. It cannot have been a war trophy. Germany under the barrel tells us it was imported into the USA likely sometime in the 20's-30's
No military markings, .30 Luger caliber or date over the chamber tell us it was not a Military pistol.
Pretty simply we know what it is not, it is not now nor has it ever been a Military pistol.

The serial number's are they all exposed or somewhat hidden?

If you do not see an obvious notch under the rear of the ladder sight at the rear of the barrel..right where the barrel and receiver join together on the top..then it is not there. If it is not there the pistol was not properly fitted for the 800 meter sight. The notch is there to allow the rear leaf of the ladder sight to bottom out. Otherwise it will rest on the top of the receiver.