O now I see, thank you for the clarifications.
This is an orthographic variant of '&'.
& is called the tironic sign, cause it is invented by tiro, the secretary of Cicero. Tiro had to use a stenographic systeme to write things really fast. So he used soms ligatures. A ligature may be seen as a combination of two letters but written together, one letter in an other. Anyway they have soms lines in commun. & in fact is an 'e' with a 't', but the 't' is written upside down and is attached to the 'e'. So this tironic sign was used in Latin for the word 'et' but also for the lettercombination '-et-' as in val& for valet, etc. Later this sign is used in other languages for 'and, und, en, et, e, ... (the words for 'et' in each language)'. In English, Dutch, ... this sign is also called an 'ampersand'. This is because the English used to end their alphabet with 'x y z and per se ent (and)'. So this 'and per se ent' became ampersand / ampersant.
& is only one form for writing this. In other writings it has an orthographical variant that looks like a 'z'.
If you want to figure out abbreviations in manuscripts, their is a little book for that:
Dizionario di abbreviature latine ed italiane, by Adriano Capelli.
This book gives 531 pages of abbreviations in Latin and Italian manuscripts and their sollutions.
Moerus (in a paleographical mood)