According to a thread from the comp.sys.tandy newsgroup (posted in 2003), the 1000AX was only sold at Wal-Mart stores during the 1980s, and similar to the 1000 SL or TL, but lacking some capabilities or features. The "Tandy 1000 Series FAQ" at oldskool.org only mentions the 1000 AX once, saying that it is rare and similar to the 1000 SX. The SL, TL, and SX all had five expansion slots, less than 1MB of memory, and processors running at a speed of 7 or 8 MHz.

The 1000 series of computers were manufactured during the 1980s and early '90s. They included several models with 8086/8088 processors and special TGA 16-color graphics (SX, HX, EX, etc.), a 10MHz 286 (RLX), a 386 (RSX) with VGA graphics, and others.

Related Newsgroup Thread
1000 RLX Details & Links