From the "Discriminating General's Muskets and Bayonets":India Pattern Brown Bess Musket. This lighter and shorter (39-inch barrel) musket became the preferred musket of manufacture by the Board of Ordnance for the British Army in 1797. Prior to this, this pattern was developed and adopted by the armies of the East India Company, hence the name. Throughout the Napoleonic Wars nearly 3 million of these brown bess muskets were manufactured and distributed to Britain's infantry regiments. The only change in their manufacture during this period was the switch from a swan-necked cock to a reinforced style in 1809. The model offered here was the more common swan-necked style. Aside from being a pound lighter and 3 inch shorter barrel, the main differences from the previous "Short Land" pattern and the India pattern were ones of style (removal of the thumb plate and only three pipes for the ramrod instead of four). Because of the numbers manufactured, this pattern saw use as late as 1850 in the British army and militia.
Very good site.