Entwicklung series The " Entwicklung " series , more commonly known as the E - series , was a late - World War II attempt by Germany to produce a standardised series of tank designs . There were to be standard designs in six different weight classes , from which several specialised variants were to be developed . This was necessitated by the extremely complex tank designs that had resulted in poor production rates and mechanical unreliability . The E - series designs were simpler , cheaper to produce and more efficient than their predecessors , however their design involved only modest improvements in armour and firepower over the designs they were intended to replace , such as the Hetzer , Panther G or Tiger II - indeed , most of the lighter E - series vehicles were intended to use what were essentially the Tiger II ' s steel - rimmed road wheels for their suspension and were meant to overlap each other as on the Tiger II - and would represent the final standardisation of German armoured vehicle design where the American M26 Pershing , the British Centurion Mk 3 and Soviet T - 44 tanks , which would have been the " Entwicklung " series ' E - 50 and E - 75 heavy tank contemporaries and likely opponents . E - 5 . The E - 5 was supposed to be 5 - 10 tonnes in weight and form the basis of a family of light tank s , reconnaissance vehicles , tank destroyer s and armored personnel carrier s . E - 10 . The E - 10 design was developed as a replacement of the Panzer 38 ( t ) and the designs based on it . The 38 ( t ) chassis was enlarged and redesigned . This new design was to be called PzKpfw 38 ( d ) , d standing for " deutsch " ( " German " ) as opposed to ( t ) for " tschechisch " ( " Czech " ) . The designs based on this new chassis would all be in the 10 to 25 tonnes weight class . The intention was to create several new light tank destroyers as a replacement for the Jagdpanzer 38 ( t ) , as well as a new family of " Waffenträger " armed with heavy anti - tank guns . E - 25 . The E - 25 designs , in the 25 - 50 tonnes weight class , were to be the replacements of all Panzer III and Panzer IV based designs . This family would include medium reconnaissance vehicles , medium " Jagdpanzer " and heavy " Waffenträger " . E - 50 " Standardpanzer " . The E - 50 " Standardpanzer " was intended as a standard medium tank , replacing the Panther and Tiger I and the conversions based on these tanks . The E - 50 hull was to be longer than the Panther , in fact it was practically identical to the King Tiger in overall dimensions except for the glacis plate layout . Compared to these earlier designs however , the amount of drilling and machining involved in producing these " standardpanzers " was reduced drastically , which would have made them quicker , easier and cheaper to produce , as would the proposed conical spring system , replacing their predecessors ' complex and costly dual torsion bar system . Other sources shows that a variant of the narrow fronted ' Schmalturm ' designed for the Panther Ausf . F would have been used , coupled with a variant of the 88 mm L / 71 gun . As indicated by its name , the weight of the E - 50 would fall between 50 and 75 tonnes . The Engine was an improved Maybach HL234 which had 900 hp to 1200 hp with supercharging . Maximum speed was supposed to be 60 km / h . E - 75 " Standardpanzer " . The E - 75 " Standardpanzer " was intended to be the standard heavy tank to be used as a replacement of the Tiger II and Jagdtiger . The E - 75 would have been built on the same production lines as the E - 50 for ease of manufacture , and the two vehicles were to share many components , including the same Maybach HL 234 engine . The E - 75 would have had much thicker armour however , and in fact compared to the Tiger II the E - 75 had improved hull armour all round . As its name indicates , the resulting vehicle would have weighed in at over 75 tonnes , reducing its speed to around 40 km / h . To offset the increased weight , the bogies were spaced differently than on the E - 50 , with an extra pair added on each side , giving the E - 75 a slightly improved track to ground contact length . According to some sources , the similarities between the E - 50 and the E - 75 went further ; they were to be equipped with the same turret and 88mm L / 71 or L / 100 gun , along with an optical rangefinder for increased long range accuracy . German scientists and engineers had successfully designed a " Schmalturm " , narrow - front turret and infra - red lighting and sights for use on the prototypes of the Panther Ausf . F as the war drew to a close . Other sources however , indicate that the E - 75 was to be fitted with the much larger Tiger II turret , which could be adapted to accommodate an even more powerful high velocity 10 . 5 cm gun . Many sources indicate that the E - 75 had 185mm – 80mm of armor . The original complex suspension by torsion bars was simplified with bogies . The standard Tiger II turret was equipped with 8 . 8 cm KwK 44 L71 gun . The engine was an improved Maybach HL234 which had 900 hp to 1200 hp with supercharging . E - 100 . The E - 100 was to be a superheavy combat tank designed to be the replacement for the prototype - only , Porsche - designed " Maus " , with the E - 100 developed from an enlarged Tiger II chassis . It was to be fitted with a slightly modified turret from the " Maus " , although plans also existed for two further turret designs . Development and building of a prototype E - 100 started in 1944 but was largely abandoned after Adolf Hitler ordered an end to the development of the " Maus " . Only the chassis was finished . It was taken to the United Kingdom for evaluation purposes and eventually scrapped . The turret of the tanks had three versions . One was a Tiger II version , another was the Maus turret , the last one was the Krupp turret . The Maus turret housed 150 or 170 mm KwK gun + secondary 75 mm KwK gun . The Krupp - designed , original turret for Porsche ' s " Maus " design housed the deadly 128 mm KwK gun , and a secondary 75 mm KwK gun . The Tiger - Maus Variant only had a 128 mm KwK 44 L / 55 ( 75 rounds ) . Armour was 240mm - 40mm . Post - war development . After the war , The French designed and built the AMX - 50 series of armoured fighting vehicles , which used a 1000HP Maybach engine with rear drive , as had been intended for the E - 50 and E - 75 , whilst the idea of external Belleville washer suspension - which was also developed with the Entwicklung series in mind - resurfaced on the Swiss Panzer 61 .