The canister may either be improperly assembled, based on your description, or perhaps it's not an AC unit? This diagram shows the correct "internals" for an AC canister. Note the spring goes on top of the filter, not underneath, and there is a single spacer bushing with flange at the bottom (red arrows). When assembled, the spring is held captive on the top bolt (which has a groove that engages the spring).
Also, I have a Purolator aftermarket filter canister on my '53 (installed long ago by a former owner). It takes a shorter filter than the AC canisters, but is easy to spot the difference, since the center bolt has a wing-nut style "handle" versus the hex head on the AC canister center bolt.
