it will be pretty obvious. pull the gantry over and get a look at the bottom the heads, look at the capping station, does it look like washed out ink or thick dried up ink, the ink tanks should be empty, etc. if the printer was decommissioned than there should only be signs of washed out residual ink, not dark/bright ink stains etc. that said, uv printers don't sit that well, also you can always just fill it with flush and then print flush onto a sheet of aluminum to get a test print. just shine it in the light. if the heads performed a test print correctly, you will be able to see it on the aluminum.