Yamasaki/Congo is active since quite a long time.
Older than some other well established japanese brands.
I have seen uncoated lenses, single coated, and also multicoated (like a 500mm tele that recently sold on Ebay.de for very good money).
I guess that all modern lenses are multicoated. If i had to place my bet, i'd say from at least the mid eighties.
The 90mm is more or less a knockoff of the Wide Field Ektar, so i don't expect that there would be a huge difference between them.
Even their tessars are said to be very close to the Kodaks. Many people think that the reincarnation of the Commercial Ektar was the Ilex Paragon/Caltar, and that when Ilex ceased the production, the f/6.3 Congo was very close to being the twin sister.
Between the Congo and the WF Ektar, i'd go for the latter, because i'm more a collector type, but if i had to choose a backpacker's lens, light and dependable, i would never choose a lens with soft single-coating, and with a big, old, clunky shutter!

BTW, i have recently seen a 90mm Congo on Ebay, for just $100.
Search completed auctions, maybe it didn't sell.

P.S.
With some luck, it is possible to find other double gauss wide angles (Leitmeyr and Meyer Aristostigmat), in a rather modern shutter. Only single-coated, though.

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