This finish is completely normal for a G.Gibbs Mannlicher or Mannlicher-Schoenauer. You have to know how these rifles were made. Until 1905 the Austrian Arms Factory in Steyr did not sell any sporters. They never sold any actions only or barreled ations. Instead, they sold their complete, finished export military rifles to all comers. George Gibbs, Bristol and other British gunmakers bought these military rifles and sporterized them to varying degrees. This rifle was completely disassembled, converted to takedown, resighted and restocked. As Gibbs removed the military sights from the barrel, soldered on his own front and rear sights plus sling eyes and engraved his address, it was of course necessary to reblue the barrel, but not the action. The trap grip caps were bought in from specialized Birmingham makers and came already case hardened.
In this old thread you may see a Gibbs – Mannlicher takedown with the same treatment of finish: Trap grip cap case hardened, action and barrel blue.
http://forums.nitroexpress.com/showflat.php?Cat=0&Number=236665&an=0&page=8#Post236665
BTW, in some of the photos you can see the backed out front action screw of the Gibbs takedown procedure.