Fender amps made after 1953 had a date code stamped on the tube chart located on the inside of the cabinet of self-contained amps and inside the amp head on piggy-back models. Sometimes the factory stamped the tube chart code onto the amp chassis too. Look for two small letters in rubber-stamped ink but be sure not to confuse the date code with the production number, the model number, or the serial number.
The first letter indicates the year of manufacture, starting with "A" = 1951, through to "O" = 1965. The second letter is the month of manufacture, starting with "A" = January, through to "L" = December. For some odd reason, "G" is not included in the month coding.
Example: If your amp has an ink-stamped code of "GD", is would have been manufactured April, 1957
Fender had another date code system for early-60s speakers and amp chassis. If the speaker is a Jensen (most pre-CBS Fenders used either Jenson or Oxford speakers), the code stamped onto the speaker would start with 220 (Jensens company code) and then followed by a three digit code.
The first digit after Jensons company code indicates the year of manufacture starting 1951. The second two digits indicated the week of manufacture. So a speaker stamped 220122 would indicate its manufacture of the 22nd week of 1951.
If the speaker is an Oxford (Fender used Jenson and Oxford speakers for Pre-CBS amps), Oxford company code was 465 and the last three digits were coded in the same way as the Jensons.
One thing to keep in mind is that both companies repeated the same numbering every decade. So you would have to guess whether the speaker was made in 1951 or 1961. A "2" (manufacture in 1952) could mean the speaker was made in 1952 or 1962.
Fender also used another code system for early-60s speakers amp chassis too. You may see something like "AB 0763" on a speaker. It's easy to see that this would be the 7th week of 1963.
Speakers are more confusing to date than the amps. Also, the speaker date should be earlier than the amp date. If not, that tells you that the speaker may not be the original. Which is becoming very common these days.