Clone makers: very possible they are all the same. See below.
The 936 is one of the few all made-in-japan things I find today. I haven't opened mine to find if its PCB is still made there, but it does have 'made in japan' marked on the casings of its components.
The 936 first appeared in the late 1990s? 97? and no look alikes appeared until mid-2000s, ~ 2004-06; this matches a google search on terms and the year the terms first appeared.
~ 2007/8, Hakko filed suit in China against the 2 factories that together produce the "Aoyue" products, and won for copyright infringement. There are more suits listed here:
http://www.hakko.com/english/company/ip/ip_news.html#news7IMHO, the technology in the 936 base is fairly basic, and can easily be copied; the real tech part is the alloy used in its tips, and are more distinctive of Hakko. Hakko has also been slow to enforce its intellectual property.
So, based on the above, I think the Hakko 936 was originally designed and all non-clones built, by Hakko in Japan.
There are many 936 look alikes, but none say they really work a like. I think so many clones are a reason Hakko phased out this model.
I always thought there is only one or two clone manufacturers, and they just print whatever brand you like on the enclosure when you buy in volume.
BTW, I never saw proof that Hakko was the original developer of the 936