Shown below is a picture of the camshaft and crankshaft timing gears originally used on the G28T Model B style engines produced by Ford-Köln in the 1940s and 1950s for use in German Ruhr & FK trucks, and Claas Mähdrescher agricultural combines.
This is the only Model A & B style Ford timing gear I am aware of which uses two cam gear marks, one for the spark timing pin and a different one to align to the crankshaft gear.
Pictured here is the original special camshaft timing gear B-6256-A5 used on the Ford-Köln G28T engine. This is used with a standard A & B crankshaft timing gear. The crankshaft gear is identical to the normal Model A & B style.
The G28T B-6256-A5 camshaft gear is different from the typical style. It has a hash mark located where the normal Model A and B timing pin dimple would be located. The dimple for the timing pin is moved 9-1/2 camshaft degrees "after" the crankshaft gear timing mark.
A special G28T timing gear was used in conjunction with the Ford-Köln front timing gear cover. The Ford-Köln timing gear cover is functionally the same as a Model B timing gear cover, having the timing pin hole 9-1/2 degrees advanced from the Model A pin hole position.
The result of this odd setup is that the Number One piston is at TDC when the timing pin is in the dimple when using a Model B front cover and this G28T camshaft gear. In other words, it is the same effect as using a stock Model A cover with a stock Model A & B camshaft gear.
It is not readily apparent why Ford-Köln chose to create a special new B-6256-A5 camshaft timing gear with two timing marks rather than use the pre-existing Model A covers and pre-existing Model A and B camshaft gears. The most likely explanation is that the lower generator pivot location on the Model A cover was not compatible or desirable for use on the later Ford-Köln chassis used in various trucks through 1954.Photo courtesy of Justin Bicknell
Ford-Köln chose to use one common timing cover (Model B) and a different camshaft gear (G28T), whereas Dearborn chose to use create different timing covers (Model A and Model B) and use one common camshaft gear (for Model A & B).
The G28T cover is also identified by the letters F-K (Ford-Köln) cast in the outside surface above the crankshaft nose. It is functionally interchangeable with the US Model B timing cover.
The G28T did not use a Model B style distributor with its odd advance mechanism and adjustable point cam. Instead it used a conventional Bosch distributor which was timed by rotating the body, and which was retained to the head by a crowfoot like a modern distributor. I believe it was for this reason that Ford-Köln wanted to set the initial static timing point at the familiar TDC piston position via the pin, rather than at the odd 19 degrees BTDC as used on the Model B.
Thus Ford-Köln was able to change and modernize the distributor design type and improve the ease of timing adjustment without redesigning any of the other engine parts.
The G28T distributor timing utilized the familiar Ford pin-in-the-hole method to find TDC, combined with the conventional timing adjustment method of rotating the distributor body, rather than rotating the point cam position on the distributor shaft to change the ignition timing.