Later issue coins such as the 2 you have posted Dato contain very little silver if any at all, they are called Potin Tetradrachm.
Your coins are fine, no worries there.
I am struggling with the legends on both coins unfortunately Dato, using what I know I am pretty confident that coin 1 is indeed Diocletian, Milne 4845 & coin 2 is Probus, Milne 4531.
Do a google search for - Alexandria Tetradrachm, then click on
www.wildwinds.
Diocletian & Probus are at the bottom so use the side bar, the rest don't matter unless you want to find your Trajan.
I have an Antoninus pius I will dig out and take a picture of, it looks silver but only contains around 25% which is called Billon.
Regards
I deny nothing but doubt everything, opinions are made to be changed, how else is the truth to be gotten at.