1934 -1939 The pre-war era under the leadership of Charles Plimpton
On launch Charles Plimpton launched not 1 but 5 sets these where simply named Set 1, Set 2 etc through to "Set 5. These sets where designed to built on each other so that Set 2 contained all the parts from set 1 plus extra parts. This followed a system used by another Liverpool toy maker Frank Hornby who organized his Meccano sets in the same way 30 years earlier. It meant that both plimpton and Hornby could make use of conversion sets so the child who initially started with set 1 could by adding 4 conversion sets end up with a set 5
The bricks were initially brown and white, the bases brown, the windows dark green, and the roofs brown. Charles began advertising Bayko in Meccano Magazine from September 1935, Regular advertisements appeared in the magazine over those next 25 years. An ideal relationship as Bayko and Meccano more complimented each other rather than competing.
In 1935 three Ornamental Sets A, B and C were introduced that contained decorative parts to supplement the existing sets, including pillars, arches and curved bricks and curved windows. These where not intended as sets in themselves but to supplement the main sets. In 1936 a Set 6 was introduced, a much larger set than Set 5 that included all the new ornamental parts. Rather than the bricks and roofs being in Brown these where in Oak, which was relatively rare and highly prized among collectors today,
In 1937 a new colour scheme was introduced of red white and green, this was destined to continue throughout the rest of the Plimpton era up until 1959. By 1938 all the existing sets were relaunched and replaced by a new series of six sets that incorporated new parts the new colour scheme.
Production was interrupted in 1942 by World War II when the company switched to manufacturing for the war effort.