Hot-Hed temperature indicator

Head paint on a McCoy Red Head .35 is also a temperature indicator.  



Seriously though, nice find, Levent.        I didn't know such existed 40 years ago. Today, one can buy an electronic temperature reader for under $25. Back then though, they were expensive and beyond a hobbyist's means.

Your post reminded me of this, but in reality the darkened Red Head paint I got used is most likely painted with the wrong paint by a previous owner.    

Back then we were coming out of the slide rule era. I bought my first scientific calculator, a Texas Instruments TI-58 programmable calculator for college, cost me $104 + tax. ($402.02 today). I was on my own. Some of the kids whose parents were supporting them asked me why I didn't buy an Hewlett Packard calculator. Those cost $400 ($1,546.25 or €1,360.68 now). One got a then new Ford Mustang convertible for college. I was riding a well worn 1971 Honda CB100 motorcycle.