I become DEEPLY suspicious of modelers with clean, well organized work spaces.
I'm not sure either, but I do like that Type 21 model. Revell of Germany brought it out in the early 90's in it's original wartime configuration as U-2540, with a cut away hull and interior, kit 05078. She was scuttled at the end of WW2. Raised in 1957 and recommissioned with extensive modification as the Wilhelm Bauer.
It was reissued in 1993, kit 05081 without interior and the hull without the cut away. That one came with baseplates for the U-2518, U-2536 and U-3501. The former was surrendered to the French and later served in the French Navy as the Rolland Morillot, including in the Suez Crisis.The latter two were scuttled at the end of WW2 and not recovered.
Reissued in 2006, kit 5004 without interior. Baseplates for U-2502, U-2514, U-2540 again, U-3501 and U-3504. All scuttled or sunk in harbor by bombing at the end of the war.
Reissued again in 2010, kit 05072 as the Wilhelm Bauer configuration as a Federal Navy research sub, with a new sprue for the different sail.That's the fine build above.
Last reissued in 2011, kit 05078 again, wartime configuration with the interior.
Wilhelm Bauer was sort of the John Holland of the Kingdom of Bavaria, 1822- 1875.