[Arran]

Well the model 620 and 610 do not have a shadowmeter but the model 660 and 665 do have a shadowmeter. The shadowmeter, if still functional, works kind of like a magic eye tube where there is a shadow, viewed through a little window of slot just above the dial, that narrows when the radio is tuned to a station and widens when it isn't. The dial lens should have a clear window right at the top of the oval, if it doesn't then someone swapped a 660 chassis in place of the original 620 chassis. This may or may not be a problem in that the escutcheon and dial for the 660 may have more viewing area then the 620 since it has four bands instead of three, maybe Ron or someone could tell you if the escucheon from a 660 or a 116 would physically be larger too.
Regards
Arran