With Rolex Japan invoice dated 28 July 2004 for the change of the bezel, amounting to Yen 2,100.
The present Explorer II model is from the very first series of reference 16550, introduced into the market in 1985 and replacing reference 1655. It features the much sought after ivory dial, also called "rail dial". The name is derived from the warm ivory-colour of the dial in conjunction with the symmetric division of the two lines below the centre: "Superlative" and "Officially" to the left, clearly separated by a vertical space (thus "rail"), and "Chronometer" and "Certified" to the right.
For a "standard" version of an Explorer II model with off-white dial, ref. 16570, see lot 99 in this auction.
The "ivory" or "rail" Explorer II models were produced in a very small series only and are considered highly collectable in today's market.