I just ordered a 25-50 off Amazon for $559, which is cheaper than I've seen it anywhere. It's odd, in that it is listed as a 20-50, but the order shows 25-50. May be some catch, but it's supposed to be delivered Tuesday so I'll know by then.
I'm about 90% sure it's a fake based on the pics and the comparison to current lenses. It will be interesting one way or another, but maybe not as interesting if I can't get a refund.The eye piece pictured based off the visible serial number was manufactured in 2001. H71 = 1930 + 31= 2001. So that could be old stock that has been collecting dust someplace.
Or it begs the question, were the 25-50x eye pieces even manufactured in 2001? I am unsure. My STS 20-60x65 nonHD was manufactured in 2006. I also have an STS 65 HD manufactured in 2019 with the 20-60 and 25-50. All of my eye pieces have their serial numbers starting with V. So they could be European manufactured or simply fakes.