All available information must be taken as a whole, and, combined with some general tips and observations provided below, a narrow range of probable production years can be arrived at which in many cases will be accurate enough for most people's desires.One thing to remember in this chronological quest is these instruments were built to be played, not (in most cases) to become museum pieces.
Some specific examples are cited that can be used to provide assistance in identifying the production date of similar components. Tung-Sol 6550 tubes have the following format: XXXYYWW, where XXX is the EIA manufacturer code, YY is the last two digits of the year and WW is the number of the week in that year.
There are a number of visual cues: anything with a foil CBS ID tag is post 1966, anything with a metal tag is prior to 1966.
The typewritten silver foil tags appeared in the mid to late 70's.
Don't get too hung up on searching for temporal coordinates to the exclusion of the unit's real purpose as a musical instrument.
Some of the component parts of Hammonds and Leslies have EIA codes printed on them.