If you have any 433.92MHz RF controlled devices then Jim's suggested test may tell you whether your ProntoPro sends 433.92MHz or 418MHz. However, I don't think you'll find codes for this in the files area. X-10's RF protocol has 256 addresses and 6-7 function codes which makes for more than 1500 codes. My extensions to that protocol add about 70000 additional codes.
The link below lists some 433.92MHz lighting systems. CodeGen™ has the codes for X-10, Philips SBC Power Control System and Elro AB600. You will need to make certain that you've properly programmed the Pronto to send RF.
[Link: mbx-usa.com]If you have access to the RF2IR half of an X-10 Powermid, I
think (but am not sure) the LED will blink when it receives RF. However, you will need to be sure it's a 433.92MHz version of the Powermid and not the older 418MHz version that was formerly sold in the UK. I
think (but am not sure) the 433.92MHz version will have a CE compliance label while the 418MHz model will not.
The radiated power level is very low. Measuring the RF frequency directly requires some fairly sophisticated equipment.