Type 99 Stocks

Gents,

Can anyone point me to a reference, on line preferably, on how to identify Type 99 stocks? Using on line references, I'm able to identify the rifles I have by arsenal and series (Kokura 23 and 25) but am not able to find out how to ID a particular stock correct for a given arsenal and series. Certainly, just looking at a stock can tell you if it is late or early due to the shortcuts employed in the late rifles, square or round cleaning rod latch, etc. but all the others look pretty much the same to me.

TIA,
VG