Is it like
this one on Flickr? He says it's a NOS 1988-1991 model. It's worth seeing the photos, I can't link them here.
That one has the same high and low stop method that my 2005 Veloce uses.
The left screw, low gear/big cog, hits the end plate at the red arrow. The high gear/small cog screw is similar, hidden behind the cable clamp at the green arrow. Is yours different?