I recently acquired an Ica Volta 146/1, which came with three plate holders. When I opened the package up for a look, I naturally examined a holder, and pulled out the dark slide. Inside, I found a light coloured thing which, on subsequent examination and removal turned out to be a glass plate. That plate is now hopelessly fogged of course, but the other two holders have not been opened.

I'm trying to work out what to do with the plates inside (there are plates inside - each holder weighs 139g, and the removed plate weighs 33g). The notable difference is that the dark slides on the unopened holders are held in place with tape - the one that I opened had no tape on it.

My options appear to be to assume they have already been exposed and develop them, or assume that they are unused and I thus expose and develop them.

The only clue I have is the existence of the tape holding the dark slides in place. Is it possible that there was some usage convention, where one loads the plates and then tapes the slides in place to indicate that they are unused? Sort of like breaking a seal to use them. Or could it be the converse, where a dark slide is taped once the plate has been exposed, to ensure that the plate isn't exposed twice? The logic works either way, but perhaps there was a convention at some point regarding how this was done. Any clues would be much appreciated.

I'm aware that I could develop one plate and see if there's an image on it - if there is I assume the other plate also has an image, and develop that too. If there isn't, I assume the other plate is also blank and expose it first. Ideally, though, if the tape means the plates are unused, I'd like to have the opportunity to expose both of them.

On the subject of exposing and developing... What sort of emulsion speed should I be using for exposure? And what about developer and developing time? Assuming the plates are ortho, can I develop by inspection with a standard red safelight (albeit kept away as much as possible)? Is a film developer like HC-110 okay?