Homebrew PCBs

So, I carelessly placed an order for a toner cartridge. It wasn't until 
after completing the order that it finally dawned that "MICR" wasn't a 
random acronym. It stands for Magnetic Ink Character Recognition, the funny 
characters printed at the bottoms of bank checks. Apparently, I'll shortly 
be able to print my own check stock.

Does anyone know what benefit MICR toner might have for toner transfer use 
in making circuit boards?