I do not know what 'exact' type of box I have, other than its one of the first 'updated' BE3-5's (with reverse on the bottom right instead of the cable and top-left)
Looking at my parts list, I can only see a complete set, nothing is showing for individual gaskets.
I actually want the end cover gasket (between the tin end plate and the main housing, the one with the level plug in) , as mines leaking a bit too much.
I thought about sealant and making one but given its thinness it seems easier to buy one as it will not be that expensive and certainly easier and less messy than making one.
This is actually a Peugeot question, although I wanted to post in the Citroen forum as it will apply equally to these too (sorry!, if you want to move it that's fine)
I can grab a pic if required, basically the gasket between the tin(ish) end cover really on the first (1991) of the 'reverse at bottom right' BE3's.