TG Consoles Under Construction at EMI Research Laboratories, Hayes, Middlesex.

An EMI publicity photo from the early 1970's, showing two Mk3 consoles being assembled.

A power supply unit sits on the trolley to the left, whilst a spare main cassette sits in a cradle on the floor, lower right.

Obviously a posed picture, since the man on the right clearly doesn't know that the cassette is inserted at the top first.