[JPBrecheisen]

My guess is somebody modified it at some point like they did with mine.

That axle should have a 22137x spindle on it. The later spindles will bolt right up when changing to disc, but the bronze bushing that is supposed to support the outer axle stub boss has the wrong I.D. The outter stub will not fit. If the spindles are a 7XXXXX series number, and has a needle bearing in place of the bronze bushing, its later model stuff somebody made fit. It can be done, but it takes some engineering. The fill plug on the back of the knuckle housing also has to be changed to a female type vs. the stock male type to clear the brake caliper.

There are a few threads on putting disk brakes on the closed knuckle 44-5Fs. Mine was set up that way when I got it, but I decided to go back to orginal drums.

You could have a "one-off" item there, but chances are, somebody just updated it at some point. The locking hubs are a later version also.

Jonathon