The short antennas were primarily used on Canadian AFVs in Germany...such as the Leopard C1 and M113A2 TUA. When all the equipment returned to Canada after the Germany close out the antennas were retained until such a time as spare parts (antenna mounts and antennas) began to become a parts/re-supply issue.
I would say of the Leopard C1s I commanded in Canada about 50% had the short antennas. They worked just the same as the standard two piece antennas and didn't need to be tied down. They also were a blessing to have when putting up and tearing down cam nets in a hide.
There is no current 1/35 short antenna...but be patient and you might see a set soon.