I don’t know.
I’d say those who were there during alpha testing? (They got “tester” banner in their profile)
Those from CBT (Closed beta testing) I also considered vets…
Or just really “ancient” players…
As for myself I joined right after the end of CBT. So… Enlisted’s start.
Yet many players who joined last year have more played matches than I do.
I’d say… it depends.
I will say years of plays will be a better metric than a fixed one like pre merge. Because time passes, new rookies will eventually become veterans. During CBT era people who participate close Alpha test can be seen as veteran, During OBT, those CBT players becomes veteran. Now those pre merge players can be consider as veteran. After a few years, those players who join post merge can also be consider as veteran.