All of us with the vintage 'dual pane' windows suffer from that inner film degradation...
There's much written about this subject here...do a search to find the threads...
It's a real time consuming, rivet bending task to take all the windows apart, clean and reconstruct...
I chose to install some heavy outside, static cling type window tint to cover em' up... It only lasts about a year or two, though...
I've thought of trying some perforated vinyl as used on vehicle wraps to stick on the outsides of the windows - maybe have it printed in an aluminum color to match the outside skin - kind of different...