As murcery thermometers are increasingly difficult to get and especially difficult to ship we have found a supplier with spirit thermometers, and comparable accuracy.
Blue Spirit filled
Certicate of conformance and accuracy per serial number and dated.
+25 to +45 Celsius, 0.1C
Thermometer is 195mm high.
so when inserted in oil bath the assembly will be about 210mm high, locate it in a sensible place within the incubator or other object being tested.
Made in Germany
This thermometer has a 'oil bath' jar included.
Leave the thermometer in the incubator for an extended period, i.e hours and hours or a day and check the temperature. This will indicate what temperature the machine keeps whilst evening out any small glitches and the like. So the oils has very slowly heated up to a consistent level and the thermometer will read that level. If you are know how, you can then use this to calibrate your machine with confidence.
Of course you should check this thermometer against others but it is a highly accurate and precise instrument.
All such thermometers should be stored upright and not put through temperatures higher or lower than there capacity.
In transit gaps can occur so thoroughly check the themometer before use and 'fix' the gaps as needed.