Early 1960s Gottlieb pinball machines like this 1961 Egghead pinball machine that I recently restored, have skinny lockdown bars that are held in place with wingnuts.
The tilt switch on this 1961 Gottlieb Egghead pinball machine was a mercury switch (glass is broken). Lift the front of the machine and the mercury completed an electrical contact. Later machines replace the mercury switch with a rolling ball tilt switch. Also present is the common pendulum tilt switch which is common on most pinball machines going forward.
Also notice the sides of the cabinet are made from strips of wood, not plywood.
These early pinball machines used five balls and each ball was manually lifted up to the shooter lane. Later games recycled a single ball (and allowed 3 or 5 ball games) but these early games dropped five balls into a holding area and you could visually see how many balls were left to play.
