Sorry Gents,
I should have checked closer. According Wikipedia (not the best source of info) there was an M4A3E4/M4A3(76)W and an M4A3E8/M4A3(76)W HVSS. I changed the text to red for the derivative I think we have. I'm sorry for yesterday's misinformation.
From Wikipedia:
US M4 Sub-Types
* M4- Continental radial engine; welded hull; 75-mm and 105-mm versions only. Users: US, Britain, Poland, France (one vehicle). Some very late M4s had composite cast/welded hulls (cast hull front identical to M4A1 (76) W.).
o M4(105) - Upgraded with 105 mm M4 howitzer.
o M4(105) HVSS - M4(105) w/ HVSS.
* M4A1 - Continental radial engine; one-piece cast hull; 75-mm and 76-mm versions built. Users: US, Britain, South Africa, France (small numbers), China
o M4A1E4/M4A1(76)W - Upgraded with 76 mm M1 gun.
o M4A1E8/M4A1(76)W HVSS - Upgraded with widetrack Horizontal Volute Spring Suspension (HVSS), fitted with the 76 mm M1 gun.
o M4A1E9 - Unknown configuration, possibly an upgrade of existing M4A1s with 76 mm guns.
* M4A2 - Diesel-powered; welded hull; 75-mm and 76-mm guns. Users: USSR (M4C), USMC, France, Britain, Poland. No US Army combat use.
o M4A2E8/M4A2(76)W HVSS - Upgraded with widetrack Horizontal Volute Spring Suspension (HVSS), fitted with the 76mm M1 gun.
* M4A3 - Ford GAA V-8 engine; welded hull; 75-mm, 76-mm, and 105-mm guns. Users: US, France (small numbers), Nicaragua (small numbers). The M4A3 was the preferred US Army vehicle.
o M4A3(75) - M4A3 w/ 75mm M3 gun.
o M4A3(105) - M4A3 w/ 105mm M4 howitzer.
o M4A3E2 Assault Tank - postwar nickname "Jumbo"/"Cobra King" - extra armour (including 4" on front), vertical sided turret, but about 3-4 mph slower. Built with 75 mm gun but frequently re-armed by the using units with 76-mm guns. Grousers fitted to the tracks. Users: US, France (one vehicle)
o M4A3E4/M4A3(76)W - M4A3 w/ 76mm M1 gun.
o M4A3E8/M4A3(76)W HVSS (Easy Eight) - Upgraded with widetrack Horizontal Volute Spring Suspension (HVSS), fitted with the 76mm M1 gun. The new suspension allowed for more armor to be added.
o M4A3E9/M4A3(105) HVSS - Upgraded with widetrack Horizontal Volute Spring Suspension (HVSS), fitted with the 105mm M4 howitzer.
* M4A4 - Chrysler A57 engine; welded, lengthened hull; 75-mm gun only as-built. Many re-armed with British 17-pounder guns ("Firefly"). Users: Britain, France, China, Lebanon (Firefly), Nicaragua (small numbers).
* M4A5 - No US vehicle was built with this designation; the number was meant to signify Canadian production.
* M4A6 - Diesel engine; composite cast/welded hull lengthened similarly to the M4A4; 75-mm gun only. Only a few dozen of this variant were built and none were used in combat.