Hustler 12 1/2" Mower Blade ?

I have come across 171 12 1/2" long (measured diagonally) mower blades, that is 57 pairs of 3.
I can not figure out what these blades go on ? i know they are for a Hustler / Excel mower but I'm not sure what model.
The # stamped on the blade is XL787150 when ever i research that number i don't come up with anything ? It's like the blade never existed.
Can anyone tell me what these blades go on?
Thanks for any help and info