They don’t make ‘em like this any more
I've recently inherited my grandmother's microwave. This baby dates back to the early 1980s (Granddad managed a branch of Currys, y'know), and while it's in working order, any writing on the front declaring its wattage has long since worn off.
The manual (yes, she'd kept it all those years) claims it's 1100W, and, impressively, a quick measurement with the digital power meter confirms that it still draws that plus a bit extra for the turntable/lights/control circuit.
Here's to never letting anything go to waste (one of many things she helped teach us)!