If I recall correctly, if two or more are hired on the same day, whoever punches in first will be the senior.
I remember a scuttlebutt many, many, many moons ago (may have dreamt this). It had to do with a bunch of mechanics making a lateral move over to drivers (might have been Indy) and retaining their senority. Guys with some serious time in service. A huge Kerfluffle ensued. Many a current driver received the "bump down". I remember a policy change of going to bottom of list if a job title had been changed. Yet I have heard one to many tales of people getting the shaft by lateral movers. What I see happen alot, is people quitting instead of asking questions. That would be sweet, next time one of the W&I gigs opens up, I mean, I can bump the number one guy, get that sweet "AM" spot, and be all eight and skate.
Solid twelve to fourteens. With new cut times and a late return due to cleanup vias, losing seniority due to late start time. Then eating another late via and doing it all over again the same way the next day.