Model: Speedmaster Reference: CK 2998-6 Date: Circa 1961 Movement: 17-jewel gilt Cal.321 manual wind, Glucydor balance, column wheel chronograph, No.18645704 Dial: Black, luminous baton hour markers, white outer 1/5th second divisions, subsidiary dials at 3, 6 and 9 for seconds, 30 minute and 12 hour recording, polished dagger hands with luminous inserts, centre chronograph hand Case: Brushed and polished tonneau form, screw down back, inner cap, fixed bezel with black tachymetre insert, twin chronograph pushers Strap/Bracelet: Fitted stainless steel Omega link Buckle/Clasp: Signed folding clasp, stamped 4 61 and 7912 Signed: Case, dial & movement Size: 40mm Accompaniments: Omega box 注脚 The reference CK 2998 was introduced in 1959 and there were noticeable changes made to the case design that were distinctive to its predecessors, this included the introduction of the black acrylic bezel. The following years witnessed far more subtle changes, which are less easily identifiable, and that might only be differentiated by the length of the hands or the scale on the bezel for example. These changes were defined by the number after the hyphen in the reference number inscribed on the inside of the case back. The current example is a 2998-6 which features the much admired calibre 321, straight lugs, tall baton hour markers and a low 'Swiss Made', as well as small pushers.