Buttons engraved/embossed with numbers 1-16. Compatible with the Pocket Operator case: http://www.thingiverse.com/thing:1375818
The "v4" version are the same buttons as included with the Pocket Operator case.
The "v4wide" version of the buttons has a larger diameter (0.5 mm) and less fillet. Depending on your printer these may not be able to move freely in the button guides of the case - I recommend trying the standard version first.
Note: A version of case, buttons and light guides optimized for SLS/SLA printing also available at shapeways: https://www.shapeways.com/shops/cdb.