For any Italeri/Revell/Meng/Takom Leopard 1
Turned aluminium barrel - with rifling - plus resin counterweight and fume extractor
This is the basic 105 mm L7 gun used on all early production Leopard 1s - and indeed on many other types of tank:
Some of the tanks above may have been sleeved, but if you are looking for a naked L7, this may be your answer.
The flat at the end of the barrel is on the left (looking forwards).
Part 1 has a weld which should be positioned along the bottom.
The fume extractor should be positioned 30.5 mm from the base of the barrel ~ see above.
A few reviews can be found here (MSC Review Connect), here (MilitaryModelling.info) and here (Armorama).