Ikke uventet synes jeg, at dit valg af en Speedmaster Professional er et godt valg
I dette link (iøvrigt fundet på Ω Link Centralen):
Speedmaster “Moonwatch” Movements .... omtales de forskellige kalibre, også 1861:
Starting in 1997 Omega changed the content of the movements it has put into the Speedmaster Professionals in two immediately noticeable and significant ways...
The movement was plated in Pink gold to begin with, then yellow-gold from 1992, then rhodium-plated in 1996.
In 1996 the movement was renamed and re-launched as the c.1861 and is still manufactured today.
A single part was changed from a metal component to a nylon-like synthetic part which wears better and is self-lubricating in all calibres except the display back model,
with it the original metal part is retained because Omega didn't want display-back owners seeing the synthetic part.
Additionally, a single additional jewel has been added bringing up the jewel count up to 18 from the 17 in previous calibres.
Kaliber 1861 er altså kaliberen, der produceres i dag. Forskellen fra 861 til 1861 er at værket nu er rhodiumplatineret og ikke gyldent, og antal lejesten er øget fra 17 til 18.
Om Rhodium og lejesten: Læs i kapitel 4 i "Ω Link Centralen".
Ref. nummer betyder urets model nummer. Dette skal ikke forveksles med
kassereference nummeret, der går på en bestemt urkasse.
Flere forskellige modeller kan dele den samme kasse.
Jeg tror næppe der er specielle "faldgruber" ved køb af Speedmaster Professional. Uret er jo robust som bare pokker

Der kan være en "overraskelse" i, at et nyindkøbt brugt ur kan være servicekrævende. Det koster typisk 2300-2500 kr.
God fornøjelse med jagten på en SPM PRO - eventuelle spørgsmål "flager" du blot op på Ω Forum.
med venlig hilsen - Geodoc