TL;DR: The final production version of the Leopard 2, equipped with upgraded armor and a more powerful round
The production of Leopard 2s for the Bundeswehr was carried out in 8 batches (“Baulose” in German). Throughout this production cycle the Leopard has been steadily improved in terms of electronics, firepower and protection. All those upgrades / innovations were included in the final production batch which began in January of 1991 and ended on 19th of March 1992 with 75 state of the art MBTs entering the ranks of the Bundeswehr.
Combat weight: ~56-57 tons
Protection: “C-technology” composite armor package for hull and turret, “D-technology” heavy and light side skirts
Armament: 120mm Rheinmetall L44 (42 rounds), two MG3A1 7,62mm machine guns (6600 rounds)
Mobility: MTU MB 873 Ka-501 12-cylinder Diesel engine producing 1500hp @2600rpm
Optics: WBG-X night vision / thermal sight for the gunner, stabilized 360° periscope for the commander
From the 97th vehicle onwards in the 6th batch the Leopard 2A4 was equipped with a new and improved composite armor package that greatly enhanced protection against both kinetic and chemical energy threats. The hull armor is identical to the later 2A5 and 2A6 versions many players are already familiar with while the turret front also gained a significant boost in protection that allows it to effectively stop many of the APFSDS projectiles found at and even above its rank and battle rating.
To improve the protection of the fronal arc the sideskirts were also improved. The new Leopard received new sideskirts that now also covered the upper hull. These new parts are easily recogniseable by their flat underside once again being identical to those found on the Leopard 2A5 and 2A6.
Estimated protection against KE projectiles (credit to @SPANISH_AVENGER)
This Leopard 2A4 retains the well known L44 cannon, but adds a new KE projectile. Alongside the DM12A1 and DM23 you are already familiar with this vehicle is equipped with the DM33 round which was put into service in 1987 and can already be found on the Japanese Type 90 and Italian C1 Ariete in WarThunder.
This round allows it to engage enemies with more confidence since it not only allows the reliable penetration of some lower tier opponents (e.g. T-64B hull armor) but also has an easier time against weakspots that might have required a very precise or lucky shot before.
There is not much to be said here, the Leopard 2A4 (1991) retains the great mobility of the first 2A4 variants.
Placement in the game
This vehicle would perfectly fill the gap between our current B-tech 2A4 that is functionally identical to the very early 2A1 version (irl differences between them don’t affect WT) and the top tier 2A5/6.
Placed at 10.7 or maybe 11.0 (with DM43) this is a relatively low effort addition for Gaijin that not only fills a large BR gap in the German high tier GF tree but also perfectly fits into the meta with its well balanced mix of firepower, protection and mobility.
“Leopard 2 - sein Werden und Seine Leistung” - Paul-Werner Krapke
“Leopard 2 in der Bundeswehr” - Frank Lobitz