AR88 resistor marking confusion explained

[Yorkie]

Just a little snippet which might be of interest.

I spotted a cutting from a magazine (don't know which or when printed), among various bits of paper I've collected over the years. It explains confusion that arose when a reader was restoring an AR88D and queried the values of resistors as shown on the circuit diagram. He cited 33M and 680M, realising that this clearly didn't mean 'Meg-Ohms' and probably mean K-Ohms, but he wondered why. The answer to his query was that up to the early 1940s, it was the practice of some sections of the American radio industry to use 'M' to indicate thousands - as with Roman numerals. For millions, they used 'Meg'. Thus a 680M resistor is actually 68,000 Ohms, and a 10 Meg resistor would be just that - 10 Meg.

Usually it will be fairly obvious from the circuit whether it's meg-Ohms or Kil-Ohms, but for circuits where there are no resistors above 1 Meg or higher, it might not be so obvious.

Hope that's of interest to collectors of American vintage radios, test-gear etc..