Brown Timber Walls and Trim

Hello All
I was hoping some one could help answer a question.
Many Years ago I lived in Wollongong and the house had ply wood walls and timber trim with old school plaster on Ceilings.
some walls and trim where painted and others a brown finish.
The painted wall had the same under the paint all brown.
One day i visited a neighbor and their whole house had the same ply wood walls and timber picture rails and timber trim around the windows and doors.
The big question is what would the walls have been finished In?
I think the houses would have been built in 1940s or may be earlier they where all timber frame.
Thanks and sorry for the essay.
Poppys.

Shellac with a stain mixed in

Photo's would help but pretty sure Ray has hit the nail right on the head.

Either shellac with stain mixed in or brown shellac (not commonly available any more).

:U

the house I grew up in had similar brown coloured picture rails and architraves.
I'm sure dad said the trim was silky oak was finished with shellac. Almost certainly the brown stuff mentioned by Neil.