NB: not a Colt M1911 (get a clue made, seriously). Stoat
Designed by John Moses Browning, it utilises a 'swinging link' connection to disengage the bbl from the slide. The Browning GP35 in British service uses a modification of this method using cammed surfaces rather than the swinging link.
On request from the American forces the M1911 was slightly modified in 1926 to the M1911A1. Changes included an arched mainspring housing, longer tang, clearance cuts made on the receiver for a more comfortable trigger reach, a longer smooth-faced trigger, a wider foresight and the diameter and rifling of the bbl, Also lacks a 'Hair Trigger' as found on the Browning 9mm and the Berreta 92F.
In service for over eighty years until replaced as the issue pistol in a contentious and highly politicised decision by the Beretta 92.
The '1911' is also made by various arms contractors, The one pictured is an AMT .45 Longslide, A Colt 1911 clone with an extended barrel.
Comparison of a few specs.
L9A1 Length: 8" - Bbl: 4.72" - Wt: 1.9 lbs - Capacity: 13 rd double staggered magazine - Mv: 1250 fps (nominal) - Calibre: 9mm x 19 - Bullet wt.: 115 gns (FMJ ogive)
(This is a rough guide, there will of course be some differences due to projectile weights, powder types etc.)