Print these in decent quality as the rotation of the Kaleidoscope will work much better with high quality prints.  I printed these slow, taking ~12 hours to print all 3 parts in black PLA

I bought 2" x 6" glass mirrors off of Amazon for $15 for a 10pack.

Use scotch tape (thick tape like masking tape won't fit in the housing) to tape them in a triangle configuration

Slide the mirrors into the kaleidoscope - it is a tight fit, wiggle them around to get it to go!

Look for the triangles to align this and slide it on.  It should rotate freely.

I used silver dollar coin holders as the specimen holder.  These are ~$2 each, can be bought online if you search for Y-65 Capsule 65mm.  Here is one source. 

Assemble the disk with the 3D printed spacer - this allows for more room inside and also stops the disk from closing completely, which is great for protecting coins but I found it super hard to open it up again. 

You may want to cut some circular tissue paper as I've done here to line the disk, as it makes a nice background for the items in the disk.