Help with unknown fuze

[Ph@ntom]

Hi, i need some help to identify unknown fuze. It have two rings.
There are points from 40 to 74 and inscription "ZUSATZLADUNG" on the top ring.
And it have points from 6 to 66 and inscription "T5ct M15" on the bottom ring.
This fuze was found at West Ukraine.
Please, sorry for my bad English.
Your prompt reply will be highly appreciated.

 

[Alpini]

"T5ct M15"

It reads 7,5 cm M.15 which is the designation of the fuze. It was used on the "Granat-Schrapnells" for the austrian Skoda 7,5 cm M.15 Mountain gun

 

[Ph@ntom]

Thanks.
8cm M.14 have 1 ring
10 cm M.15 also have 1 ring.
But 7.5 cm M.15 have 2 rings. Please, can you explain me why it's so?