A good old PS / 2 keyboard is one that's not USB port can get up and running on one, it is sufficient not a simple, purely mechanical adapter, but there are USB-PS / 2 converter for about 8 to 15 that this can accomplish, however, like to have their little problems with special characters. A very good Converter there are, for example, by the manufacturer Lindy.
=> With a few niche products there are few scenarios where this purely mechansiche adapter can function at all.
Here it should be noted on the product page again express. Probably the Verküfer actually speculated with the fact that nobody ever returns the plug for 1.