On the older Retina II and III - if it is a push on filter or hood, then the 32mm diameter comes into play.
If the above photo is correct, your Automatic III does not have a provision for 29.5mm screw in filters.
The image below shows a f2 Heligon from a 1949-50 Retina II. Look by the H in Heligon for the barely visible 29.5mm filter threads.
, on Flickr
- Andrew in Austin, Texas -
35mm Gear Bessa R, Leica II, - IIIg, - M2
Just for fun 35mm Gear a Kodak Retina IIa, a Rollei 35 S, plus a Voigtlander Vito II and Vito BR
Modern Medium Format Fuji GW 690III
Vintage MF Folders a Voigtländer Perkeo II and Bessa II, 2 of them - a ZI Mess Ikonta 524/2 - plus an Agfa Super Isolette & a Record III
Digital a D300 and a D700 with some primes - still going over a decade later
"Who spilled the Dektol on the bathroom carpet?"