The Tru-Beat ref. 6556 was introduced into the market in 1954, fitted with calibre 1040, a modified and more sophisticated version of the well-known calibre 1030. Aesthetically similar to a normal Oyster Perpetual, the major difference of the model was the dead beat sweep seconds hand: instead of continuously sweeping on the dial, the second hand stops at each seconds mark before jumping to the next one, performing exactly like the hands of an analogue quartz watch.
Dead beat watches were already made in the early days of watchmaking and have always been considered as the symbol for a very finely engineered watch. At the time of its introduction however, this particularity did not enjoy much success and consequently the production of the Tru-Beat was discontinued after five years.
For a Tru-Beat in gold see lot 361 in this auction.
The Tru-Beat model is illustrated in The Best of Time - Rolex Wristwatches by James M. Dowling & Jeffrey P. Hess, p. 202.