[Herald1360]

I can't see why anyone would want to do this after production. The original type valves would not have been unavailable even if some accident had taken out the filaments on several of them at once (the only reason I can think of for multiple valve replacements}.

There are two versions in RM- one with American types and the other with Osram types so a third with miniature types doesn't seem unlikely. Maybe there was a cost saving even using extra grommets and adaptor plates.