If there are or are not partial stampings on the barrel rib, plus none on the right side of the barrel, it is not likely to be original. There are a few guns out there that seem to be original without the stamping, but only a factory letter will tell you for sure. The 5th Model 32 Bicycle Gun was offered in a 2" barrel, but law of averages are if you are paying a big premium, chances are that it is not original.
When you see the gun, pay extra attention to the top rib, refinish, and the slot where the front sight is attached. I cannot see a pin through the rib and am certain that the factory would not have soldered or driven the front sight into the slot. Standard 5th Models have an integrally forged sight with the barrel, but Bicycle guns were pinned. Good luck.