Guys, do yourself a favor and dont buy used
colorimeters. Munkis, spyders, variations of i1display, including latest "Pro" and similar. They do not age well and will produce errors. If you don't trust me, here's the same info from the horse's mouth:
Hi, Typically how long will a colorimeter last for if kept at room temperature and used 3 or 4 times a year. What is the procedure w/ DisplayCAL to determine if it's time to replace the device? Thanks.
hub.displaycal.net
If you just want to play around and learn new stuff, sure, a colorimeter for 10 Euros will allow you to fire up a calibration apps and see how they work. But otherwise, it's just like buying a used condom in the hope that it can still be used.
Better save some money and buy used industry standard i1Pro
spectrophotometer. It operates on different principles and will last forever. Except the lamp for reflective measurements, of course, but for display calibration, it's not needed. These can be had for as low as 50-100 sometimes, depending on location, condition and what's included in the set. New they were 1k-3.5k.
For display calibration a plain unit will do. If display mount is not included, you can make an improvised black foam surround yourself to block the scattered light and can always hold it by hand.
P.S. Don't buy OEM versions of i1Pro by EFI. They have custom firmware and are not recognised by regular apps.