1. Does anyone know how the city of Tuchola would have been spelled in a road sign in 1939.
Spelling of this town name - if you mean polish language - same as today - Tuchola. German name for this town is Tuchel, but in 1939 Tuchola belonged to Poland.
2. Is Koronowo the modern name for Hammermuhl where the 3rd Pz div Crossed the Brda ?
No, german name for Koronowo was "Polnisch Crone" or "Crone an der Brahe". The 3rd Pz Div crossed Brda (german "Brahe") at Sokole-Kuznica village ("Hammermühle"), about 12 km north of Koronowo.
3. The bridge east of Tuchola is that the original bridge ? the upside down looking bridge
You mean the bridge which was used by part of the 3rd Pz Div to cross the Brda river here?
Its name was Rudzki Most (Rudzki Bridge). First it was wooden bridge, then in early 30-ties new concrete bridge was built.
The old bridge is on first and third photos, the new one is on the second picture:
And for some clearance. The largest city in vicinity was Bydgoszcz (my home town
). Then 20 km north - Koronowo. Next 12 km north Sokole-Kuznica and next 20 km north Tuchola with Rudzki Bridge.
Jim, here you'll find some more info on the subject: