All 105.003s have a year iteration, -63,-64 or -65. There are differences esp the lug profile. The -64 is a smooth curved lug, the -65 has a bevel or chamfer.
The website above has all the info you need for a start. Is this a watch you own? Few free to post some pics.
Well really it’s the reverse. The Ed White is really a 105.003-63 but people refer to all 105.003’s as Ed Whites.
All 3 iterations are considered to be Ed Whites, Lt Col White I believe wore a -63 iteration on his space walk in 1965 (or was it a -64, I forget) but the others are called the same thing since they are so similar. Note different case makers were used so the marks differ across the models. There is no such thing as a ST105.003 without an iteration code. But there is a 145.003-65 though. ps it looks like it was a -63 on White's wrist (2 of them in fact) if this Fratello article is to be believed: https://www.fratellowatches.com/why-ed-white-wore-two-speedmaster-105-003-watches/#gref
Posted photos in reply to Davidt post ref. To my original question I wanted to know if there is a difference between the S and the ST
Well the case maker differs between the -64 and -65 (HF for the -64 then FJ? for the -65, nobody seems to know) so the marks do look rather different, but if you are asking do they have a different meaning, AFAIK they both indicate that the case metal is steel. Omega used a 2 letter code scheme for the metal from at least the 60s onwards, I think the single S was a precursor to this. Letters seen after the case number like 'SP' can have other meanings (eg to do with water resistance) but in this case I think both codes are just referring to the metal and are perfectly standard. Cofusingly Omega used a prior 2 letter scheme for metal up until the late 1950s where stainless steel was coded CK so you will find lists of metal codes that contradict each other. Here is an inconclusive thread on the subject: https://omegaforums.net/threads/anatomy-of-an-old-style-reference-number.76789/