I thought it was Olivetti making DEC's PCs during the 286-through-Pentium era?
From my understanding during that time in the USA DEC PCs were made by Tandy and in Europe by Olivetti. Sometimes a Tandy-made DEC PC could have the same name as an Olivetti one despite being completely different machines.
Below is what I found about the Olivetti-made DECs...
The DECpc 425i is an Olivetti M300-30
The DECstation 200 is an Olivetti M250
The DECstation 220 is an Olivetti M250E
The DECstation 300 is an Olivetti M300
The DECstation 325 is an Olivetti M386/25 (and possibly the "325C" as well?)
The DECstation 350 is an Olivetti M380 XP1
Then those ones I am not sure...
There might have been a "DECstation 210" that once existed...
The DECstation 320 is probably an Olivetti M300-10?
There might be a DEC-rebadged Olivetti M300-08 also known as a DECstation 300 or 320 (or both?)...
The DECstation 425 sounds like it was an Olivetti M486 (it could've been a CP486 as well or an LSX 50xx but an M486 is the most likely)...
The Digital Venturis systems (at least the majority of them) definitely have an Olivetti-like case but I do not know if they were actually manufactured by Olivetti... I also do not know if they were re-badges of Olivetti systems or if they simply used similar-looking cases and put unrelated motherboards inside of them.
There were also DEC re-badged Olivetti laptops like the DECpc 425SLE, which appears to be an Olivetti Philos laptop.