The grandfather of the Bullet was first produced by Royal Enfield in 1931: a four-valve, single-cylinder engine was introduced, given the name 'Bullet' in 1932. It had an inclined engine and an exposed valve gear.
The 1935 G model was the first that assumed the 'modern' look, with vertical cylinder, cast-in pushrod tunnel and eventually fully enclosed valve gear. It had a gear-driven magneto and double-ended eccentric oil pump.
Over the next few years the single would sport two, three and four-valve cylinder heads.
In 1948: The first 350 Bullet Roadster was introduced. Although it was similar in many ways to the 1935 G model Bullet, it was a new motorcycle with many design innovations.
It was the first British production bike with a rear swing arm. It also had an oil filter (with integral oil tank in the crankcase behind the crank) and alloy primary chain case. It was a two-valve pushrod design in semi-unit style, with gearbox bolted to crankcase. Rubber kneepads were on the gas tank. It had four gears (one up, three down like most British bikes of that era - apparently Triumph was the oddity with high gears up). A Trials/Scrambler model was also introduced.
1949 The sports model had an unsprung front mudguard.
1951: Modifications include smaller front mudguard and silencer, alloy speedometer nacelle and modified fork ends.

Today Enfields are made in India using all the old dies and machinery they bought from Britain.
Methinks you would have to be brave to buy one . . . .