Some weights that are interesting to know.

Display has one decimal place, so that 442 = 44.2. The display does have a decimal point, but it doesn’t show at the angle of the photos. Sorry.

This is an Uno R3. I don’t suppose the old Uno weighs much different.

The weight of the block has been tared, in case you were wondering if I forgot, which I have been known to do.

Interesting conclusion: Adding an Arduino (not including trays) will increase the mass of the robot only by less than 20%.