Good grief; I said it was embarrassing.
Ratbert is quite right, there is a "Display" button on the front panel. I'd done a scan of my programmable buttons & decided it had been configured without a Display function. It's the small one above the On / Off, for others similarly shackled.
And Richard W is also right; Function + Display on the MSR does indeed scroll through the display fields on the G61R that I remember from my 568 days, including blank, so thanks to both of you.