@Jubadub, in answer to your question regarding the old mercury thermometer… I needn’t tell you to be careful? But personally, I’d try it. And a couple of things - given that those usually required 3 minutes to measure a temperature, maybe insert it @ 10 minutes and wait until 13 minutes elapses before reading?
Also a warning to keep your eyes on it (perhaps behind a face shield) in case it exceeds 107˚ which was their normal top temp range,
when it might actually explode. So, don’t let it get that high / hot.
[However, if you’ve re-pasted your heatsink, it’s unlikely that it might get that hot in 10-13 minutes anyway.] One other minor thing is that their low temperature measurable range likely may not register at, or even below 76˚.
I no longer have one of those mercury thermometers because I’d like to test that too. And given the time, I might eventually try a “related” laboratory thermometer because they have an extended range. (Around $10.00.)
Have also considered the newer, 30 second read-time digital thermometers - but they too have a limited temperature range.
And just as I won’t spend the higher prices for a G4 mini these days, I won’t suggest that anyone spend any money on other temperature meters, but I did find one for about $10.00 less than I paid for a dual meter, which might just suit the purpose, should one wish to purchase one. $18.89
https://www.amazon.com/Thermometer-Thermocouples-328%C2%B0F-2501%C2%B0F-Thermocouple-Temperture/dp/B0D5M27WZY?ref 

Still looking forward to Bolkonskij’s findings and any other temperature reports from others that might follow.
Now again, back to testing here.