When you look at the circuit board of these meters they have a ZTxxx type number, probably because they are all made by Zotek.
I agree. The facts on this and other meters suggest that Zotek is the manufacturer; and Aneng, Bside, and others are sales and marketing companies.
I've noticed that there's a weird dull patch on the plastic just below the "OFF" position on my AN860B+. It's also present on the other brands, eg. You can see it here in joe's review of the Kasuntest variant:
This makes me think they
all come out of the same machine.
Edit: Yep, it's on the Zoteks, too. I can see it in Youtube videos:
(OK, not easy to see in that frame but it's very obvious in the video. I wanted a frame where you could see the splodge
and the Zotek branding at the top which isn't easy when the cameraman is insane).
DoubleEdit: Also Zhiaoxin brand: