Can safe. The internal dimensions are roughly 2.25 inches diameter and maybe 7 inches deep (60 D x 180 mm)... wide enough to fit credit cards.
I used a "safety" can-opener to remove the bottom of this can. They allow you to replace the top (or bottom) of a can, and use it as a lid, and there's no sharp edges.
My can opener is described in this other project. $6. https://www.thingiverse.com/thing:3056479
Both the end-cap ring, and the internal ring, were attached with hot melt glue.
For good results, you want to be accurate. To be inconspicuous, the end-cap is to be perfectly centered. Take care assembling it.
I'm sure these files can be scaled up or down somewhat, to fit similar sized cans. The diameter of the inside of your can determines how much, if any, to scale.
I'd print a small, quick experimental ring to determine the required size. Then scale the internal and external rings together, so they still match each other.
On this Afinia H479, the pieces used 16 grams ABS, 45 minutes, 0.30mm layers, with raft.
Metric files provided in case your software thinks an inch = a millimeter.