Tohl Narita: “I think this was remodeled from Nelonga. I made it look like another monster by hiding its face rather than fiddling with every part of the costume. Therefore, when the lids flip up, Nelonga shows up.”
In my post about the making of Magulla, I referred to an explanation that Nelonga was remodeled into Magulla by applying a removable spiny surface to the costume before Magulla was converted into Gavora finally.
Given the episode in which Magulla appeared (#8 in production order) was produced after this Gavara episode (#7 likewise), however, the costume might have been eventually converted into Magulla in reverse order rather than Govora.
Nevertheless, as it is least likely that the Baragon costume borrowed from Toho was remodeled so much as Magulla with spines all over the body, the removable surface might have been applied to Magulla for real.
Above all, it seems to be unlikely that the horn Nelonga characteristically had was removed for Gavora and put back for Magulla while all of these are so confusing and deepens the mystery.
It was Akira Sasaki who sculpted the flip-ups and attached them to Gavora, and he says in a book it was very hard to adhere the fins (made of FRP for the white parts with urethane for the red parts) to the costume so as not to come off.
Although the spines of Magulla were also sculpted by Sasaki, the connection between these two monsters is obscure unfortunately as it is an old story.
Furthermore, Sasaki says two heads might possibly have been made for Govara: one with the closed fins and the other with the opened fins so that one can be replaced by the other.
The sculpture of the fins is excellent and the concept that the monster shows its real identity after opening the flip-ups is very much attractive anyway.