Re:
The M008 shifters are just the same as XT M739 and M740 shifters. In some respects they are more like the M739 shifters in that they don'y have the removable indicator window, but the Shimano sticker covers the holes where the indicator as seen on the M740 would attach. So kind of a bit of both.
I think they appeared around 1999 as a 'non series' 8 speed shifter option.
Good shifters with very little difference in terms of feel and action when compared to the XTR shifters.
I've always found STX-RC shifters the most reliable 8 speed shifters though from the late nineties era.
EDIT: Checked back on my initial post. The M008 shifter actually appeared in 1996 when the first V-brake compatible XT STI ST-M739 and separate brake levers (also M739) were introduced. They appear visually more similar to the shifter pod from the earlier ST-M738 STI unit which was had a cantilever specific brake lever.
So... I think that Shimano used the shifter mechanism and lower housing from the ST-M738 STI and produced a top cover/bar clamp to allow people to run them as separates. This was badged up as the ST-M008 shifter.
The following year the mechanism from the ST-M739 STI unit had it's own top mounting and was released as the SL-M739.
1996 XT groupset.