The "36" in the model number denotes nominally 36,000 BTU's per hour (i.e. a 3 ton.)
One ton of air conditioning is equal to 12,000 BTU's per hour. So, typically you find the numbers after the first couple of letters, and divide it by 12.
18 = 1.5
24 = 2
30 = 2.5
36 = 3
42 = 3.5
48 = 4
60 = 5
In 1992, minimum efficiency ratings were increased to 10 SEER, and stayed there until 2006, when they went to 13 SEER. So, unless your unit has "high eff" stickers on it, chances are it's a standard 10 SEER.
Air conditioning units have gotten so expensive, most people just get the standard model, as every number SEER increase is alot of $$$ increase.
Hope this helps.