I believe that's the earliest model- with the all blue graphics. The biggest difference will be the chips used for the delay. Some of them are noisier than others. A later rev is the holy grail, but no harm in trying it, and if it sings for you take it.
Holy Grail is reverb? Did it evolve from Memory Man or did you mixed something there?
I meant holy grail as slang, not a product name. Later rev means a later revision. The later revision of the Memory Man with the black graphics and red writing is the "holy grail" version of the Memory Man. There's a particular chip it has to have in it, though.