I've poked around the internet looking for info on these, found this so far:

From Bitsavers docs:

U59 252004-005 ROM OS Lo
U60 252004-006 ROM OS Hi

U78 253001-001 i80186
U17 253002-001 i8042 (KP Custom)
U-- 253003-001 SG Custom
U43 253004-001 RHB Custom (VLSI VC2030B)
U42 253005-001 RP Custom (VLSI VC2029) ( " CPU V3089 VC2029 VTI 48-Pin DIP Ceramic Gold " ?? )
U16 253006-001 i8042 (Sound processor)

From http://www.digibarn.com/collections/systems/mindset/

Roger Baderscher (President of Mindset) was the head of Atari's Home Computer Division from 1980-1982 and had quietly commissioned the design of a new modular computer system while at Atari, using Atari Industrial Design resources and tapping into one of Atari VLSI engineers Chris Rhode. Roger, Chris and about a dozen Atari Home Computer division engineers would leave Atari in 1982 and form Mindset, and their quiet skunkworks project would become a reality.

I've got some nice brochures and other materials I can scan and send to you, I have every module, expansion pak and controller made for the system and Chris Rhodes has promised me that eventually when he digs up his old schematics and notes he'll send them my way for the M-1001 Mindset. I also have 2 M-3000's which are the rackmount JVC'd versions of the Mindset system that JVC used in-house after they bought Mindset in 1986.

From http://atariage.com/forums/topic/42993-what-the-st-almost-was/

The ST would later have a Blitter chip, similar with the chip designed by Chris Berg (former Atari engineer) for Mindset.

http://pro.jvc.com/prof/attributes/category.jsp?productId=DISC1.8.3 and others -- Mindset hardware and software in JVC catalog