Various types of improvised armor for the american M4 Sherman tank, her crew’s desperate and often futile attempts at upgrading the hopelessly outdated armor during the closing stages of WWII.
This tank effectively stayed the same throughout the war, as upgrade attempts (like the Firefly) would meant the gigantic production output would get disrupted, a case of quantity over quality.
The Sherman had thicker armor than the PzIII and IV due to sloping.
The Firefly wasn’t the end-all be-all of Sherman variants. For one the breech was fucking gigantic and turret ergonomics. Two, the 75mm M3 gun could fuck up a PzIII and IV easily, which was absolutely fine since American forces rarely encountered Tigers anyway. Three, the 76mm M1 could frontally penetrate a Tiger I’s hull at 1,000m (the 75mm m3 could penetrate at 500m). While logistics did play a part in the design, it did not affect tank effectiveness to a substantially meaningful degree.