The box is an alteration to a box I found in a score-pal booklet that Elke sells. If you have the third print of this booklet, there is a template of a window box in it and if you use a 30x30 cm paper and score at 4-26 and 4-14-18-28 instead of the numbers described in the booklet you will create a box that can hold a theatre ticket of 22x10cm.
The stamps are from