Written by Chuck Maddox on 6 May 2001, 03:25 GMT

Last Revised: 6 May 2001, 03:25 GMT

Certain Rights Reserved...

This is a quick guide to decripting Omega Case Reference numbers which were used from roughly 1963 through 1996. Watches made prior or after these dates are likely to use a different scheme for distinguishing models. These numbers are typically found on the internal (movement) side of the case back. It should also be noted that sometimes an additional number, typically a 0 or Zero, between the third and fourth numbers. Sometimes a decimal point is added after the third number so some example caseback numbers include: 145022-74 ST, 3450803, 376.0822, etc. Lastly sometimes the year of manufacture, and case material notations are also omitted. Don't be thrown by these variations...

Case Ref. Numbers:									Description:
1	4	5	0	2	2	-74	ST		Example Case Reference Number
1	4	5	0	2	2	-74	ST
1									The first position indicates strap/bracelet material type: 1: Leather strap (men's) 2: Leather strap/diamond decorated bezel (men's) 3: Bracelet (men's) 4: Bracelet diamond decorated bezel (men's) 5: Leather strap (ladies') 6: Leather strap diamond decorated bezel (ladies') The first position indicates the material and the presence or absence of diamonds on the bezel, differentiated by men's and ladies' watches. The reference number is very convenient for parts supply operations.
	4								The second position indicates mechanism type: 0: Manual winding chronograph 4: Manual winding chronograph 6: Non-chronograph 7: Self-winding chronograph 8: Quartz or tuning fork chronograph The second position indicates mechanism type Since this Speedmaster data in most cases it indicates a chronograph type of mechanism. There are of course exceptions like the c.1045's...
		5							The third column indicates supplemental function type.  5: No date 6: Date 8: Chronometer The third position indicates the presence or absence of date display, chronometer grade, and other supplemental functions. Chronometers are always listed as "8" whether they have a date display or not.
			0 2 2						Differentiation of various models: These individual numbers do not designate anything specific, but are used to distinguish between the various models produced...
						-74			Year of Manufacturer...
							ST		Abbreviations for watch case materials: Code: Description: BA BC BG BT DA DD DG DL MD SP ST TA TI TL Yellow gold White gold Pink gold Platinum Yellow gold combination Gold combination Pink gold combination Gold combination Gold plated Strap Stainless steel Titanium and yellow gold combination Titanium Titanium and pink gold combination   Note: Sometimes this code is stamped before the case number…
1	4	5	0	2	2	-74	ST		Example Case Reference Number
1	4	5	0	2	2	-74	ST

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Disclaimer: Opinions are my own and knowing me should be taken with a grain or two of salt...

-- Chuck