Bath has two routes 37.
First's 37 from Bristol via Bitton.
Coachstyle's 37 from Malmesbury via Acton Turville (one return journey on Wednesdays)
And a bit of a tenuous one, but Bristol technically currently has two 506s.
They are both run by Bristol Community Transport (CT Plus).
The long-standing 506 has been split in two at the City Centre, pending the withdrawal of one half when metrobus starts. Until then, both halves are known as the 506, the soon-to-be-withdrawn one being a free shuttle. In both directions, one stops where the other starts.
And if you do include prefix/suffixes then in Bristol we have the 3, 3a, 3b, 3c, 3x, m3 (from 27/5), x3, x3a, a3 and ag3.
The oddity here is that the 3a, 3b, 3c and 3x (Wessex) are in absolutely no way related to the 3 (First), as they are the four variations of Wessex's own erstwhile 3 which was closest in route to First's 309/310 before they became the 78/79 (which are now becoming the T2 and massively re-routed and expressified T1...