For such a large aircraft, the 747 had a very benign stall, even demonstrating a gentle nose down moment at the stall which is unusual in a swept wing design, most of which have a nose up pitch moment. Boeing considered a pusher or shaker unecessary. The early 100 series airfrmes delivered to US carriers had neither. However, while being certified for the UK register, the CAA's test pilot on the aircraft decided that some sort of artificial warning was needed. So the shaker was added, and Boeing considered that it was a good measure to include it as standard equipment thereafter as it wasn't a complex or expensive modification. This is why it is a simple elecetric motor with an eccentric weight attached to the control column by jubilee clips - and looks like it's been designed by Heath Robinson.
Incidently, the test pilot was DP Davies, author of 'Handling the Big Jets'.