[AMRadio] OF memory erasure

[CL in NC]

OK, can someone confirm that the standard rack panel used to be ID'd with letter designations, i.e. 'A' was the narrowest, and possibly up to K or L at 21 inches?  Now the 'U' unit is used, a 1U panel equivalent to the A and up from there.  I have not been able to find the letter sizes explained on any internet site, only the unit size 'U' designation is explained with no historical reference to the letters.

Or was I in a fog for 54 years of messing with this stuff.

Charlie, W4MEC in NC