Did you try moving the stem in closer to the car. It is held on internal knotches by a spring. I was shown how to do it by Mike (Metal Micky ).
Yes, tried that
You can't tell quality plating by looking at it, smear with salt and leave wet and if it's poor, it'll rust in days!
Guess it's rubbish chrome then...
About a year ago, I made a new set of lamps for the traction engine. I nickel-plated the (brass) bezels &, as a matter of interest, I plated a spare, which I left outdoors ever since. It's still perfect. When the mirror bases get too bad, I may well cast a couple of replacements & nickel plate them. Personally, I prefer nickel to chrome.
Ian