Olivetti 3MB ST506-interface drive?

[Jules Richardson]

Does anyone recall an Olivetti ST506-interface drive with a colossal 3MB 
capacity? Apparently a full-height 5.25" unit with 4 heads and two platters.

I'm just curious; I always thought that capacities either equaled or 
surpassed the 5MB of Seagate's ST506 after they introduced it, so I was a 
bit surprised to hear of a drive with < 5MB.

For context, Acorn apparently used them during development of their 
external Winchester units for BBC micros (Acorn SASI board, Adaptec 
SASI-ST506 bridge, ST506 drive). Production units that I'm aware of had 
either a 10MB or 30MB drive fitted (BASF typically, I think). We're talking 
1983, or maybe late '82, so considerably after the introduction of the 
original Seagate drive.

The only Olivetti drives I'm finding mention of are a 10MB single-platter 
drive and a 20MB dual-platter drive. Acorn had close ties with Olivetti, of 
course, so I did wonder if Acorn acquired some pre-production drives - but 
it seems like a bit of a leap to go from a 3MB dual-platter prototype to a 
20MB one.

cheers

Jules