Anyone can simply test for AB at an REC or sit through the class and get a cert. it is essentially a watered down 100ton test. 70% on ROR instead of 90%, no chart/plot.
As for 200t, you will not get a higher endorsement for mate. The mate 500/1600 are a separate set of requirements & tests.
Remember, if you don't have the sea time over 100 tons, you will only get a master 150 / mate 200 until you have satisfied those requirements.