[Mod: correction to text as advised by OP]
Vicente Boffo never made Fish vases at Mdina, when arrived Harris was making these with Jim Munnelly when Jim Munnelly arrived he was making these with Harris, likely also with Ettore Boffo and Said being the boy. The making of the fish vases was a team effort, here is quote from Jim Munnelly,
"Hi Wolfie, fish were a Mdina design and made in a team environment, t. member 1 blows a coloured ball picks up silver chloride, cases it and blows and shapes that into a lollipop shape with a short neck, passes that to, T M 2 who side dips in clear lifts clear of molten glass turns new dip allowing tail to fall across the face, withdraw and shape on flat plate repeat this process on the other side. Second dip was a very tricky one after the second dip the size of the piece was close to that of the furness opening plus the item had softened and that glassmaker would need to withdraw quick allowing for the downward bend.
T M 3 would then reverse onto punty reheat the neck draw cold snap top and melt to finish chip off and kiln the finished piece One person could easily do the whole thing or you could have 5 people Doing the dips was the longest part and not practical to split. When I was there I always did the dip stage, when on leave or after I left either Joey, Michael, would have be able to do it. The shape may have developed away from the status quo of the time as it did when I joined. Pappa (V. Boffo) never did it to my knowledge not because of skill, but because that was one heavy item on the end of an iron. I would say it was made when I was in the team.