I recently purchased a 1944 BF Avery model A with a two speed (underdrive ?) auxilliary transmission. This transmission looks to me like a factory option or a factory built aftermarket option. It does not look home made at all. It does not resemble the Trasco units found on the HG/OC-3's at all. It looks more like the two speeds used on the OC-4's. It does not show up as a factory option in any of the Avery or Cletrac GG parts books that I have looked through. I have spoken with two local experts and they have said that this was an available option, but did not know if it was factory installed or dealer installed. Between the two of them they had only ever seen two not counting mine. I would like to find a manual or some literature about these, or possibly a picture or two, so I can fix the shifting linkage on mine (which is missing). Any information or insight would be much appreciated. Thanks, Esev