[Hallicrafters] SX-71 - another cleaning question

[RJB]

Good morning to all

a few weeks back, i asked on this list how to clean the grime from the
chassis of my SX-71. Based on the responses i tried the Scrubbing Bubbles
(?) in patches on the chassis (not ready to do the whole thing yet). The
bubbles sure enough cleaned off the grime <thanks guys>, but i find that
there is still a dull grey "scaly" appearance to the outside of the
chassis - i have also noticed this on ebay photos of Halli rigs. I assume
this is the plating.

1) did they come off the assembly line like this?
2) or is it a patina achieved in old age?
3) is there any safe way to buff it up a little (i dont want to use
abrasives on an old steel chassis)

thanks for any advice

Bob Bennett, Maple Vly, WA