So did Guild produce the Detonator before the Liberator? If so, is it possible that they looked at the Detonator body and said; "You know, that would look much better if we slimmed it down and gave it a little more contour!". So they came up with a new body shape for the Detonator. Then they said; "You know, maybe it really should be a new model seeing how different it is and all. What do you think we should call it? Mmnm let's see, Detonator, Elevator, Excavator, Fumigator, Generator, (couldn't think of anything for H, I, J, & K.) I know, the Liberator!"
Ta-Da!
(Who needs Volume II?)