This is a case for a single audio microcassette (as used in dictation recorders and answering machines, not a "compact" cassette for music).

Present features (compared to a standard commercially-made case):

• It snaps shut.
• It locks the tape reels in position to prevent unwinding due to vibration.

Absent features:

• It probably will not comfortably fit a J-card unless enlarged, and even if it were it would not be transparent like a molded polycarbonate case.
• It does not have ridges/recess to assist in pulling open the case, but I find that the printed plastic is rough enough not to need them much.

Possible improvements that could be made:

• Compact cassette version — once I have a cassette to test fit with.
• Window to reveal labeling, at the cost of less dust protection.
• Make the .scad Customizer-compatible for tweaks.

Also on GitHub: https://github.com/kpreid/3dp-tape-cassette-case