with confirmed 3kro.
I'm not sure this means what you think it means.
Membrane keyboards (such as rubber domes, scissor switches and IBM Model M) are 2kro. This is a limitation of the technology: the manufacturer can't fit diodes to a membrane, so there is no *guarantee* that when you press more than 2 keys that a ghost won't be formed. Ghosts happen when you press 3 keys that form 3 corners of a rectangle on the keyboard's column/row matrix. The back-flow of current causes the fourth corner to go hot: a ghost. However this doesn't mean that every combination of three keys will cause a ghost. It also doesn't mean that such keyboards are limited to sending 2 keys at once to the host: practically every USB keyboard on the market supports the low-speed USB spec limit of 6 keys plus modifiers.
So what 2kro means in practice is that *some combinations* of 3 keys won't work properly, but if the designer of the keyboard has laid out the matrix and written the firmware to avoid common problems, you should rarely encounter any issues in practice.
But since the marketing materials of membrane keyboards never go into details about the layout of the matrix and how the controller is programmed, I don't see any easy way of telling if you will have a problem unless you can try before you buy, or ask someone who owns the model you want.
