QVC 3rd Volunteer Battalion Devonshire Regt 18mm button by PEARSE.

QCV (Queen Victoria Crown) 3rd Volunteer Battalion Devonshire Regt 18mm button by PEARSE.

• It started as the 3rd Devonshire Rifle Volunteer Corps in 1860, part of the wave of part-time volunteer units raised after the invasion scare of 1859. These corps were independent of the regular army and mostly middle class.
• The Devonshire Regiment took that name on 1 July 1881 and absorbed the county's militia and rifle volunteer units at the same time. Devon's other volunteer corps took "volunteer battalion" titles on 1 November 1885 (for example, the 1st became the 1st (Exeter & South Devon) Volunteer Battalion on that date). The 3rd most likely changed at the same time, so your button's wording points to 1885 or later.
• It was an East Devon battalion. Kelly's directories place its H Company at a drill hall on Castle Hill, Axminster in 1893, D Company at an armoury on High Street, Honiton, and F Company at Ottery St Mary.
• When the Territorial Force formed in 1908, the volunteer battalions joined it and were renumbered into one sequence. By 1914 those same towns had companies of the 4th Battalion, so the 3rd VB appears to have been folded into the 4th Devons, which later served in Mesopotamia in the First World War.
• White metal is typical of volunteer units, which wore silver-coloured buttons to distinguish them from the regulars' gilt.

The maker: J & B Pearse & Co, London
The "I" on the back is a Latinised "J". The firm was John Brice Pearse, with a long lineage: Nicholas Pearse & Son in 1790, J N B Pearse by 1805, John Brice Pearse by 1817, then J B Pearse & Co from about 1839 until 1924, when it became part of Compton Sons & Webb.