Im pretty sure the GRD 1 is a smaller than the GRDII, III and IV, so I'm not sure if it would fit..... Well it may
, but with a bit of room to spare!
The IV is marginally bigger than the GRD & GRD II but you can use the GC-4 case with all the GRDs. I bought my GC-4 second hand from a II user and used it on my II quite happily. The main difference in reality is that the IV is a bit taller and with the GRD & GRD II the up-down wheel is slightly buried in the lower case but still usable.
A perfect fit then - well no. Usable - well yes, and looking at the links to handmade cases at least as good a fit.