Hey, so you got it upstairs ok? It still works?
What part of the world are you in? I have a Synrad Power Wizard with a NIST traceable calibration that measures from 0.1 to 250 watts...
One way to get a pretty good indication of power is to aim the laser at a substance with a strong absorbtion of the CO2 laser wavelength (which is practically anything other than shiny metal ) and measure the heat rise over time. You could then use math to calculate the average power.
One trick I did before I got my meter was to bolt a 50 watt resistor (one of the aluminum housed gold colored ones) to the underside of a piece of black annodized aluminum (black annodized aluminum absorbs 10,600nm fairly well, and aluminum is a good conductor of heat). I then attached a thermometer (actually a thermocouple hooked to my multimeter) to the annodized aluminum block, fired the laser at the block and took note of the temp reading after a certain amount of time (like 10 seconds). I then let the block settle back to the starting temperature and powered up the resistor with a certain current (to get a certain wattage) and noted the temperature after the same amount of time (10 seconds). If the temp was higher than with the laser, I knew the laser was doing less power than was flowing through the resistor, if lower, then the laser was doing more power. I would then reduce or increase the resistor power until I got about the same reading.
You can see why I jumped on the chance to purchase the Synrad power meter when a brand new one appeared on ebay for $200 (they retail for over $500).