So, you're confused by all these different names and numbers, and are trying to make sense of them? Here's a quick rundown of the various SAE product lines.
(Credit goes to Mark Gurries of the SAE_Talk newsgroup for putting together most of this information. Any errors are mine, and I'd appreciate your feedback if I got some details wrong. Also, if anyone has any production figures, I’d love to know that, too).
SAE had several distinct product lines:
"Mark" series (names start with "Mark": "Mark 24", Mark 1M", etc. Introduced 1970)
"00" series (product names ending in 00: 2600, 2800, etc. Introduced late 1975)
"01" series (names start with a letter and end in "01": A501, P101, etc. Introduced early 1980s)
"02" series (names start with a letter and end in "02": A502, P102, etc. Introduced mid-1980s)
"X" series (names start with an "X" designator - X-10, X-25, etc. Introduced 1979)
"Professional" series (names start with a "P" - P50, P250, P500, etc. Introduced 1980)
"TWO" series (Products labeled as "SAE TWO", sold from 1976-1985)
For both the "01" and "02" product lines, the various starting letters are:
A - Amplifier
P - Preamplifier
T - Tuner
E - Equalizer
C - Cassette deck
D - CD player (02 only)
I - Integrated amp (02 only)
R - Receiver (02 only)
Here's a (very) brief description of each product line:
The “Mark” Series was the original SAE line. The products included amps, preamps, equalizers, and tuners. The majority of the units were silver-faced (called "champagne" by SAE) with a limited number of black-faced units. Almost all the Mark series were non-rack mount. Some SAE buffs consider the Mark series the best sounding SAE ever.
The "00" series supplanted the Mark series. All the equipment was black-faced, rack mount gear. The amps got more powerful, the preamps got more sophisticated and the equalizer line went berserk with complexity. The "00" line was the most extensive product line SAE ever had, with numerous preamps, equalizers, and signal processing units (time delays, crossovers, etc.) The metered "00" amps (2400/2500/2600) were the best looking SAE ever (in my opinion) but have the annoying downside of being fan-cooled, which gives you a constant background hum when listening to quiet passages in music.
Between the "00" and the "01" series were some transition amps, the 2401 and the 2201. These were placeholder products pending the introduction of the "01" series. The 2401 is basically the same as the A501. The 2201 had no direct analog in the "01" line, but was an internally (electrical) updated 2200.
The "01" series replaced the "00" series as SAE's mainstream line. All the equipment was black-faced, rack mount gear. SAE did away with the cooling fans on the amps, which made them much more home-user-friendly. They also streamlined their preamp and equalizer line, with only one of each, and introduced a cassette deck. The "01" series saw the introduction of the "Computer Direct Line" technology, in which conventional mechanical controls were replaced with electronic servo controls.
The "02" series was a step down from the "01" line, designed to be a lower cost, more mainstream product line. It inherited the Computer Direct Line technology from the "01" and introduced a CD player, the D102. The "02" were built in Korea. They overlapped the "01" series and were sold during the last years of the "01". Following the withdrawal of the "01", they became the main SAE product.
The "X" series was SAE's attempt to capture the high end audiophile market. The majority of the "X" series were in a silver/gray finish, and were rack mount. A very limited number were produced in black finish. The "X" series was the most limited of SAE's product lines, with one preamp and three amps in the line-up. Not a lot of them were produced, and they're pretty uncommon today.
The "Professional" series were designed for sound reinforcement applications like concerts. The older 2600 had been a mainstay of the concert circuit, and the Professional series replaced it once the "01" series came out. The P500 and the P250 were essentially beefed up versions of the A1001 and A501, respectively, with balanced XLR input jacks for professional sound applications. The product line (as far as I can tell) consisted solely of amps and a forced air cooling system - no preamps, equalizers, or source components.
Finally, the "TWO" series was SAE's bottom-of-the-line consumer system. Aside from the name and some of the styling, the TWO line had nothing in common with any of the other SAE lines. Unfortunately, that's about all I know about the TWO series.
For more specifics on the SAE products, I'd refer you to jims-sae.site.com. For a complete product listing, go here. Jim also has the sales literature and brochures on all the different product lines.