Are you sure that the camera is a #1 and that the lens is a 12 cm? I ask because if it is a #1 its native film size is 120. US-made #1 Special FPKs were last offered with an f/6.3 Zeiss Tessar in 1915, focal length was 4 3/8" and the lens was in a Compound shutter.
I've seen UK-made #1 Special FPKs with, iirc, a 100/6.3 Tessar in Compur.
So the focal length seems wrong. No matter, f/6.3 Tessars are very good lenses. I sometimes shoot a 130/6.3 in Compound on my 2x3 Graphics. On 2x3 it gives up nothing to modern coated f/4.7 tessar types or, for that matter, to any of my other lenses around that focal length. Same goes for a 150/6.3 CZJ Tessar in barrel made in 1912. All uncoated, all very good. Good color rendition, good contrast, perfectly usable.
Compur shutters can almost always be cleaned, lubed and adusted. Look for a decent shutter mechanic. Carol Miller at flutotscamerarepair.com is well respected but may not be working these days, Paul Ebel, located somewhere in Wisconsin, also has a good reputation. Look around.