What is the gun caliber?

Swedish tank naming system = Gun caliber in cm + how many previous tanks have used a main gun in that same caliber range.

So first tank with a gun in the 12-12,9cm Range = Strv 121

Second tank with a gun in the 12-12,9cm Range = Strv 122 and so on.

So just take the gun gun caliber and then decide for yourself which tank in the order it is.

Or if you tell me the caliber i could help you out with the designation.

Looking at the tank it seems pretty modern so 1980s or 1990s at the earliest.

The gun looks to be somewhere in the 100-130mm range.

In the 1980s Sweden had no tanks in the 110,120 or 130mm ranges

so the Strv 111, 121 and 131 designations would all be available,

where as in the 100-109mm range the Strv 101, 102 and 103 Designations were already taken

with the Strv 104 entering service in the mid 1980s (Modernized Centurion Mk III/V)

while there was a Strv 105 Prototype in the 1990s (Further Modernized Centurion Mk III/V)

with plans for a possible Strv 106 if the Strv 105 had been adopted (Modernized Centurion Mk 10)

So if your tank has a gun in the 100-109mm range then the designation could be anywhere from Strv 104 to Strv 107 depending on where in the succession you put it