I'm pretty sure yours is a Russrep. I remember that particular one.
I agree with Chaim about it being the lighting in those particular photos. For instance, here is my unfinished saber loosely put together for a quick picture (on top):
http://i.imgur.com/HStD34I.jpg
My grenade is still covered in matte black paint/oil/whatever from over the years. The combination of overhead lighting, camera flash, and B&W nature of the photo make the middle section of cubes look bare when they are not.
However, note that in the third Chronicles photo, it does seem that some of the paint/bluing is missing from wear on a handful of cubes.
Seems saber on top is painted,because the shape of cubes doesn't seem very neat.
If real grenade,maybe it has been restored.
The worst scenario:
-found,then cleaned,I mean,grinded to a white color,painted black,and warnished
The best scenarion
-found and just cleaned using a metallic brush,by hand,and then protected using black paint or warnish
Even best
-found,uncleaned,just protected using frameto,but then,no shiny look
Seems yours may be the second one,but it's just what I can think after seeing this photo.
but bottom has no paint,easu to see not glossy,just used by hand on the cubes,no more.
The golden color near the emitter makes me think the foot of grenade was here,and the cap too.
I think the grenade was found quite soon after the war,or kept in a storage,with air rust only,no under earth rust,like actual dug items.
if dug,was dug wuite soon,if not even in the 70's it would be more rusty.
but I'm sure the grenade was rusty,because painting would have other look,and the colored rings would be visible,even on a bkacl and white photo,especially the red ring.
Serenity,for you photo,you can try to take it about one metter farther,and with bigger zoom,will flatten the image and give even closer result.