Antique Swiss Silver Pocket Watch Case - Makers Marks?

Sprinkled in amongst the three bears (correct for Swiss 0.935 Silver) this silver pocket watch case shows three castles with initials stamped - top left, top right, and bottom center in the pic. It’s difficult to be absolutely sure of the letters themselves, but I’m wondering if these mark patterns are familiar to anyone.
Much appreciated!
WATCHBACK

-chillspine

The letters are W H T but that’s as far as I can go.

Phil