I concur, that is an ISA 16 bit slot. The 8 bit version used only the part of the slot that was closest to hte edge of the board and was sized accordingly although 8 bit cards could be used in 16 bit slots.
BTW you can call me old if you want to since I am 50. Those slots go all the way back to the IBM PC AT that used an 80286 Processor. Wow, that was considered a fast machine and a fast expansion slot at the time (Mid 80's). Your system is definitely much newer since you have only one 16 bit ISA slot and the rest of the slots are PCI slots. Interestingly, the ISA slot outlasted the AGP slot by a few years because although it was slow by todays standards it was very flexible and there were literally hundreds of interface cards that were made for it - everything from standard com ports and printer ports to Graphics cards and special purpose cards like the one you have there. Nice trip down memory lane!