Aluminium metal filler

[RDfella]

There's nothing you can do (in my view) with a quantity of pin holes, apart from linishing and polishing deeper in the hope they'll come out. Chances are you'll uncover more, though. Black sheep is spot on - first job I had was in the tool room of a firm specialising in aluminium casting. Spraying with a lacquer, rubbing down and repeat may hide those imperfections, but I guess that's not the finish you're looking for. Tig welding would require the holes to be opened a little first, and there is no guarantee the area would not still have imperfections. What can be guaranteed, though, is that the filler applied by Tig will be a different shade. It'll look like its got measles. You'll have to live with it, I'm afraid, and, as others said, look out for a better casing in the meantime.

[BSA_54A10]

 Not sure about in a tube, but a long time ago I used 'Devcon' to repair(bodge) broken chaincase bosses, but it isn't cheap....and dunno if it'd polish up

 More recently there was a similar thread happening and I erroneously stated that I used 'Lumiweld/Alumiweld' to do a similar  repair(bodge), but what I used was actually a supposedly Aussie product 'Ultra-Bond', a heaty-weldy stuff almost like solder but it seemed to work well, but can't say how effective it would be on an externally polished case...or if available elsewhere

All of those fillers are solder for aluminium .
Most are zinc-lead alloys some are zinc - aluminium alloys
The zinc -lead will be closer to the colour of the Al-Si alloy.

Zinc polishes up slightly on the blue side of white.
Getting a filler that colour matches your cases is a very expensive process and if the same when highly polished will be different when dull.
There are companies that specialize in making colour matching welding rods but your are in the 3 figuers per stick territory.
Museums and fine art restorers use them all the time but by the time they have finished the "value" of your A 10 will have tripled.

The other problem with colour matching is grain size & orientation.

The trick to hiding imperfections is the type of polishing.
There are several different mechanisms.
Cutting ( auto sol ) replaces big scratches with finner scratches till the scratches get that fine you can not see them.
Using a buffing wax & stitch mops actually melts the oxide surface turning it into a semi-metallic glass and that will hide imperfections in light.
You will still see them when the chaincase is in the shadows but as soon as any light hits the surface the glassy surface reflects so much light your eyes can not see the imperfections underneath.
That is one reason why show cars are always brightly lit.