The Triumph R style was introduced to the market place in 1915 with a 1 hp engine.
There is a difference between the L and R style.
The R style offered larger flywheels, relocated cam gear, flat pushrod, single governor weight, shorter base. Decals and striping still adorned the R style but not as elaborate as the L style.
The brass nameplate did not appear on the R style, this was replaced with the serial stamped on a raised area on the top of water hopper.
Along with the 1hp engine in 1915 was the big 16hp,There was a rearragement of hp sizes in the L and R catalogs in that year, with a full catalog of R style engines on offer.
R&V ignition system as standard was the ignitor, battery and coil, with oscillating an rotating magnetos as an option right through to 1918.

All Triumph R engines could be operated to run on kerosene. Water spray was included on 4hp and larger, this was to reduce carbon deposits. The catalog states that water spray was not necessary on the smaller engines.