[KLR]

BM - bimetal
GM - gilding metal (not brass)

WM - white metal (formerly known as GS - German Silver)
AA - anodised aluminium
NM - New Metal


OSD - Officer's Service Dress (bronze badges)


blades - usually on the back on officer's badges (probably your 'tangs' !?)

loops - popularly known as lugs


QVC - Qn Vic Crown - actually used before 1837 but superseded by KC in 1902

KC - King's Crown - 1902 - to at least mid 1950s

QC - Queen's (Elizabeth II) - from mid 1950s-



OR - Other Ranks (ie not officers)


Pattern - War office / Min of Defence official / authorised pattern number for each individual badge (from the 1850s onwards...)

vertical shank - popularly known as a 'slider'


EonF - no, I didn't know this one either - seee below!