John, I found my original HP 1000 keys and they are marked 4T1427. The CAT99 keys may be for the back door of the cabinet. Many of the HP 1000s were mounted in cabinents that had locking doors on the back. I don't know what the key number was but I think they had round heads also. I do know they were made of brass and I know that they were different from the FP keys. If you don't need the FP keys I can use them. I've made copies but they're not the same as the originals and aren't as nice. Joe you're asking. But yes the keys in all of the HP 1000s are interchangeable, at least in the six or eight machines that I've tried. I don't have one here but IIRC they are Corbin keys and they are brass with a round head. FWIW I just got some keys made and it was a real hassle. I tried Home Depot, Lowe's and a couple of othe large hardware places and they didn't have any blanks of the same type. I finally went ot a small local hardware store and they found some blanks made by another company (ILCO?) that they could make keys from. The new keys have a trapazoid shaped head like that usually used on house keys and they're nickel plated steel so they look completely different from the original keys. main power switch is located under the cover. not worth the cost to ship them from the UK to Florida.