I don't have "chapter and verse", Alan, but I would go for 1992.
For sure, it featured in "Evn 149", which was published in February 1993 (where it was cited as costing £ 1,035).
For what it's worth (and as we all know) it was developed from the 3000, but was far superior electronically (and included a battery)! I would say that the 3000 (which was itself designed as a low-cost alternative to the MS-2000 - which was circa
1985, I would say) was introduced in 1990 (or maybe a year earlier).