Genuine Minolta made, never seen this before. Minolta's equivalent of Nikon's K-ring set
Likewise it was made before MD era, so the front metal ring interfare with MD lens' lug.

No.1 = 7mm, No.2 = 14mm, No.3 = 28mm: The frontal metal rings together is 5mm thick,
which is very useful for tele-photo lens for short-range usage, even for normal lenses too.
They all have odd ∅57mm thread for the extention, so hard to use as a hood or a tube.
So combinations are: 5, 12, 19, 26, 33, 40, 49, 54mm's

I made hood by using those black tubes > http://www.pbase.com/kkawakami/image/162443672