Hello Frizzen,
your shrapnells and also the austrian shell do not belong to the cases you show. The shrapnells should have 24 grooves and belong to the Krupp gun 7,5 cm M.1880. These shrapnells and the brass or later zinc / aluminium / steel fuzes are made by Krupp / Essen and sold to turkey. These guns M.1880 used bag charges and had no cases.
Is the number on case T8 a 660? This would be very interesting. And if yes, does this case have a neck or is it one of the cases seen on your other photo?
@AndyD: I got most cases of this type for free or for a very low price around 5-25 €. If it had turish characters did not make a difference in price when I bought them. The price was only depending on the seller and if he knew which is a rare headstamp. In Belgium/France and also in south-east Europe it's a very common calibre as nearly similar guns where used by Netherlands, Belgium, Italy, Sweden, Romania, Bulgaria, Serbia, Turkey, Greece.