"The movie's fictional BB gun, described as the "Red Ryder carbine-action, two hundred shot Range Model air rifle with a compass in the stock and this thing which tells time", does not correspond to any model in existence nor even a prototype; the Red Ryder featured in the movie was specially made to match author Jean Shepherd's story (which may be artistic license, but was the configuration Shepherd claimed to remember). However, the "Buck Jones" Daisy air rifle, immediately above the Red Ryder in the Daisy line, did have a compass and sundial in the stock, but no other features of the "Red Ryder" model. The guns and a stand-up advertisement featuring the Red Ryder character appeared in a Higbee's store window in the film, along with dolls, a train, and Radio Flyer wagons."
As noted above it's called artistic license. Often used in films, books, and other such entertainment-oriented media.
If you're looking for historical accuracy in this entirely fictitious story and film, you're going to be awfully disappointed. When I view the film, I see it for what it is, and I delight in the many memories it conjures up.