I bought Bausch & Lomb f10 Anastigmat (estimated FL 20" - it might be 19.75" but it's no shorter). It's definitely a dialyte lens (it all unscrews) but doesn't look like the Process Anastigmats shown in the 1928 or 1941 B&L Catalogues. From its serial number it was made 1935/6 and and it's larger than the 18" Process Anastigmat and in a similar barrel to the B&L Protar (page 12 of the 1941 cat).

An information would be great, it's going on an 18xx24 Reisekamera.

Ian