This is an exceptionally clean timer from Omega for retailing through Prestons as noted on the dial. Prestons were long-standing agents for Omega in the UK and probably their biggest distributors of timers until their closure in 2016 after almost 150 years of trading.
Each minute is divided into 100 equal parts so it would have been intended as a "process" timer as in "Time & Motion" or "work-study". Sub counter times to 30 minutes. The watch is crown wound. The slider button on the side starts, stops and restarts the timer. The crown resets it. All works exactly as it should. The dial is in unmarked condition. Only micro-scratches on the case-back where it has been put down.
Inside is the Omega 8300 calibre movement. Marked Omega 7 jewels there is a Maltese Cross stamped under the balance wheel which denotes that the movement was in fact made by Lemania for Omega (as most of their timers were). The movement is in pristine condition.