Italy Stamp With Overprint(S)

I looked for this Italy with fasces in Italian Socialist Republic, but when I couldn't find it I noticed that there was vertical overprint of ISTRA and so I looked into Jugolavia occupation stamps. But still cannot find it. Can anyone help. Much thanks for all your knowlege!

Has me stumped.
Not checkd Stanley Gibbons as yet.

exist here..............
https://www.burda-auction.com/en/pu...r-tips///48/

It is an un-issued stamp. The photo in Rod's post is of the set.
Gibbons states 'In June 1945 various stamps of Italy were overprinted 'ISTRA' and further surcharged for use in Istria and Pola (Pula) but they were not issued. However four were further surcharged and issued on 1st July.'
The 75 cent carmine was issued in July but as a 6 lira extra surcharge on your stamp.
Hope this helps.
Regards
DavidR

Thanks David.

unissued..thanks both david and
rod...somehow I think that unissued means more...thanks!