Hi Aaron, I bought them from the original owner and he had only hooked them up twice before I bought them. He told me they were 91's so thats what I believed... but yes the serial # do indicate they are not... first 2 digits are year, next is week or weeks if applicable, then the rest are the speaker number off the line. so... 87 is the year, 5 means the fifth week, and 13 is the speaker number.... just to make sure that i am correct.... the other speaker's number should be 87512 or 87514 can you check to see please(assuming they were sequential... can't remember).
and I can't see why he would have put AL XO's in a brand new pair that didn't come with AL's, but i could be wrong. I would be willing to bet that AL XO's were put in and those are all original, but because I wasn't the one who picked them up from the store I couldn't confirm that 100%. lol. Now my curiosity is peeked and I am going to scour the web for that info on the XO's : )