As you may know, Vindolanda is one of the few places in Britain where portions of two consecutive Roman milestones are still in situ and visible. The most impressive lies on the track behind the museum. But the stump of a second is visible near the intersection of the Stanegate with the Once Brewed road. You likely walk/ride/drive by it every day on the way to & from the site.
Into the 19th Century, this milestone stood to its full height, and bore an inscription recorded by Horsley in 1725 as BONO REIPUBLICAE NATO ("To him who was born for the good of the State"). Unfortunately, around 1815 the upper part was broken up and split to make a pair of gateposts!
(Information gathered from Keys to the Past)
Ive been on my usual Mithraic evidence collating and ended up at Escomb church (Escomb church was built in part from stone taken from Binchester Fort) where there was supposed to have been a part of a Mithraic altar built into the wall.....I dont know about the Mithraic connection....but
within the church on a whitewashed stone :
BONO REI PVBLICAE NATO - exactly as your Vindolanda example.
Set on its side and located on the internal North wall, it is part of a window jamb (bottom left stone) of the more easterly Saxon window. .
This inscription was not noticed until June 1969 when a schoolboy from Lanchester pointed it out.
Dated to the reign of Constantine ??