If you have 2 “Batterymen C” on the field in Attack Position, each of your Machines gains +1000 ATK. If you have 3 “Battermen C” on the field in Attack Position, each of your Machines gains +1500 ATK. (NOT +4500!!!)
A “Batteryman C” equipped to “Relinquished” is not in Attack or Defense Position so it will not be counted for the effect of “Batteryman C”.
If “Batteryman C” is changed to Machine-Type, it will itself gain the ATK bonus.