I haven't seen a TW-1 with a silver screw before. It doesn't have the long dash either. I am going for a Touch Wah right now that has the silver screw and is the real deal, but this one doesn't sound right to me.
I have a Touch Wah TW-1 that I bought in 76. The one you linked to says T- Wah on it. Mine says Touch Wah then TW-1 under it. I'm pretty sure mine was a first run of this pedal. That one seems to be newer. Mine also has a silver screw.
If you want some photos just drop me an email and I can get some for you in the morning.
The T-Wah in the link is a real one, I have a silver screw T-wah as well, and it does have the serialnumber stamped, it is something like 9500.
Anyway, this one is the real deal, the batt. compartment will probably have two holes in it.
Just noticed a Touch Wah, and this one has a stamped serial number which reads 7300 so it is a little earlier, but I guess they sound very similar to the T-Wah's.