This badge is bi-metal and dates to approximately the 50s (although it could possibly date to WWII). The badge is and is in fine condition other than some rusting on the back and some small marks in places. The very end of the slider is also snapped off, although the majority of the slider is intact.
The regiment started as the 48th Regiment of Foot in 1741. They have been honoured for their role in the Siege of Gibraltar (1779-1783) and for the Battle of Talavera in 1809. This is why "Talavera" and "Gibraltar" can be seen displayed on the badge.
In 1960, they were amalgamated with the Royal Lincolnshire Regiment into the 2nd East Anglian Regiment, dating the badge to at least before the 60s.