After doing some EXTENSIVE internet research and following up various hunches and leads (I'm getting better with my German with all this research!), I think I've finally narrowed down the true origin of the new bike.
From the beginning of this whole escapade, the green color of the bike just didn't seem right for an army issue bike.......... all of the old military bikes are painted various shades of black and olive drab, but his one is a brighter green. I knew that I had seen that color in the old German services before, but I couldn't place it exactly. Well, today it all fell into place. The color of the bike matches exactly to the old original colors for the old German Bundesgrenzschutz, or better known as the German Federal Border Guard (BGS). The time line of the early post-war BGS, matches the date of the bike as well.........
After WW2, all of the German military, police, etc., were disbanded and all of their uniforms, insignia, vehicles, paint schemes, etc., were "erased" in what was know as denazifacation. The occupying forces of the USA and Great Britain for West half and Russia for East half, took over all of the police and military functions until the end of 1948. This is when Germany was officially split into East and West Germany. The Western occupying forces decided that there was a need for a competent Federal Border Police to handle the increasing incidents along the East-West border and Czech borders. In 1951 the Bundesgrenzschutz was officially formed by enlisting 10,000 former WW2 Wehrmacht officers as the new BGS. The BGS was organized along paramilitary lines in battalions, companies, and platoons, and was armed as light infantry. It was controlled by the Ministry of the Interior as opposed to the Ministry of Defense, assuring that it was not an actual Army.
This all fits quite well with the bike having 1948 dated numbers and for having olive drab painted inner fenders and a brighter green overall paint job. The fenders are most likely earlier army bicycle fenders that were reused in the new bike. The rear rack is also not of the same type as the army versions used all over Europe up until this date. It looks like what I would call, "Post War Modern". This fits as well.
The modern German Army, or Bundeswehr, was not started until 1955 and the colors were traditional military...... olive drab and camouflage.
Compare the two pictures........... The original BGS patch and color to the color of the bike. It's about as close as you can get! I'm confident that this is the actual ID of the old bike. Early documentation is tough to come by for this period of German history, so it will be a tough research project to track down any actual hard proof, but then I always like a good mystery to research.
Here is a picture of a contemporary German Border Police vehicle and as you can see, the color has remained the same.
The uniforms for the BGS for this period up until 1955, looked very much like the WW2 versions, including the old "coal scuttle" helmet that was replaced in 1955 with a US style helmet.