Summary

These are reels for 1" tape storage and transfer, intended to fit paper tape equipment with 1/2" spindles, as per ISO standard 3692.
The tape reader photo shows an example of a machine intended for this style of reel.

The smaller side are used for a 153mm (6") reel, the larger for a 216mm (8.5") reel.

The reels can be used directly with tape by folding a few millimetres back on itself at the end and fitting that in one of the hub slots, then winding a full turn to lock that in.
Or, a tape roll with a standard 2" core will fit over the hub. To allow that to be driven without slipping, fit small strips of rubber in the four shallow slots in the hub. Those should engage with the notches inside the tape roll hub

The hub is common to both the small and large reels; the sides are twist-to-lock on the hub.
The hub is in two identical halves.
The halves can be fixed together either using:
M4 countersunk screws (drill out one side to 3.5mm and the other to 4mm, then fit 20mm or 25mm screws from the 4mm hole side).
Or,
3mm dowels, 16 - 20mm long. For those, remove the support from the three smaller holes and open those to 3mm, then push the dowels half way in, apply a small amount of superglue to one hub surface, then clamp the two halves solidly together.

Either way, ensure the slots and pins in the two halves are aligned!

Printing: The reel sides do not need any support, just print as they are, with the recessed part of the three hub latch areas upwards.

The hub needs "support everywhere" to ensure the tops of the T pins for the reel side latches are correctly formed. Remove that support carefully after printing, to avoid damaging the heads of the pins.

I used black PLA+ but I'd expect them to work OK with PETG or other mechanically suitable materials.