How to "fake" a megawattmeter
I believe you can get full scale output from this meter with 5A/110VAC input (600W). The markings refer to a situation with a 1000:5 CT and a 6000:110 PT (per phase). CT = current transformer PT = potential transformer.

It should also indicate from a single phase. So if you stick a 120V 100W light bulb on there (assuming you have a 120VAC supply available) it should indicate around 1.2 MW. Try leaving the unused phase connections open.