Q: Odd 220 pF capacitor form factor, how to read markings, what type and what for? I was recently given a bag of electronic components by a relative. These components have been bought in the late 1970s or at the latest in the early 1980s.
Among them were ten components that I initially took for 1/4 W resistors (shown in image on the left): they had the same form factor (about 6.3 mm x 2.5 mm, cylindrical with axial leads) and were also marked like resistors (shown in image on the right).
220 pF capacitors in unusual form factor (left). 330 Ω resistors for comparison (right.)

The markings were
red - red - brown(sic!) - silver - silver
If this had been a resistor, this would have been a 2.2 Ω resistor (or an oddly specific 2.21 Ω resistor, which would make no sense given the silver stripe).
Measuring the resistance gave an open circuit reading, but when I accidentally measured them as capacitors, they came out as 220 pF. I assume that the brown stripe used to be black, but that this colour has faded over the years.
My questions now are:

*

*Was this style of capacitor common in those days? Is it common now? I have never seen this before.

*What type of capacitor is this most likely?

*Since they came out as 220 pF but the silver stripe indicates x 0.01 on resistors, it seems like the silver stripe has a different meaning on capacitors, is it x 1 or x 0.001?

*This component came out of a hobbyist home computer lab in the 1970s/1980s. What do you need a 220 pF cap for in this context where the fastest CPUs had 20 MHz clock cycles?


A: Sounds like an axial-lead ceramic capacitor. 221 (red-red-brown) is the code for 220pF. The other bands are likely tolerance (+/-10%) and tempco (perhaps +/-10% over the temperature range). Eg. this data from a discontinued product.
They were not uncommon in that era, at least in Asia and to some extent Europe. North American parts of similar form factor tended to have alphanumeric markings.
