I'm not an expert but I'll share what I've got.
From the 2012 book Italian Vintage Drums and Cymbals by Luca Luciano, p119 [1st edition] there is a slightly different story.
Before the mid 1980s he worked in B8 and with UFIP and work in B8 led to the Tiger line. However, it sounds like he then went back to B20, at least for the THREE and FOUR series. Alas it isn't entirely clear in this passage what the difference between ONE and TWO versus THREE and FOUR was, but it contradicts what it says in The Cymbal Book (p168) in terms of alloy.
In the mid 1980s he leaves Ufip for building his own cymbals in B20 alloy.In 1988 Bespeco International distributed Spizzichino's cymbals with the name Spizz, whose cymbals in B20 were discontinuous, the economic ONE and TWO lines, created in 1987 and the THREE and FOUR lines in 1989.
So maybe ONE and TWO had more machine production and THREE and FOUR were more expensively produced by more hand work? I don't know. Sometimes "economic" is about the alloy, but it can be more about the degree of hand work versus machine work in shaping the cymbal. Based on what Luca Luciano says, your quote from Pinksterboer regarding B8 may not be relevant to your THREE. It might be B20. I'm not sure exactly what page you got your Pinksterboer quote from, but on page 167 Pinksterboer says:
In 1988 Spizzichino joined Bespeco International, Italy, for whom he continued producing four less-expensiv seris, sinply called One, Two, Three and Four. The B20 cymbals were discontinued. It had turned out to be impossible to survive making such cymbals in a one-man factory, at that time
Now one reading of this passage is that Pinsterboer is saying ONE, TWO, THREE, FOUR were B20 and were discontinued. Alas we're dealing with a speaker of Dutch interviewing an Italian speaker and writing a book in English. The same sort of translation issues arise with the Luca Luciano book (although it is done in both Italian and English). Can you give me the page number for your quote so I can go and check it in context without having to scan through lots of pages? *** edit *** I found it by accident while looking for something else. Page 126 and not in the index. Hidden in the section on Swiss and German manufacturing methods. Hmmmm. I've written in many additions to my index so I can find things. Anyway, that quote seems a inconsistent with the next page which mentions:
The B8 Spizz cymbals, made by Bespeco (Italy), are entirely made by automatic machines according to processes that were developed by Roberto Spizzichino.
How is it that Roberto's processes are hand hammering on the previous page and suddenly computer based machine hammering on the next page...but based on his work? I think something has been lost in translation.
The fieldwork for The Cymbal Book must have been done in 1992 or before (since that's when it was published). Since 1992 there have been other cymbalsmiths working in B8 to produce high quality cymbals. I'm thinking in particular of Johan van de Sijpe (RIP).
[ame="https://www.youtube.com/watch?v=rZdrQA435s4"]Johan VDS Cymbal Set 13" Hats, 16" Crash/Hats, 20" Ride - YouTube[/ame]
although like Roberto he worked in different alloys at different times. There is more the the sound quality of a cymbal than the simple notion of B8 = beginner/economic and B20 = professional/expensive.
It was after the THREE and FOUR series that Roberto made his trip to Wuhan, China, which resulted in the whole "Spizz" brand name being abandoned by Roberto after unapproved copies started coming out of China. This gave cymbals with "Spizz" ink a questionable name, but yours would seem to be from the earlier (pre China) period.
If you have some other B8 and B20 cymbals you might compare them to see what the color of the alloy looks like. I'd be interested to know since the references so far seem inconsistent as to the alloy used.