HUBLEY Ahrens Fox Cast Iron Fireman Engine Driver

This was my latest pickup from an Estate sale in Dallas. This estate had lost s of watch and clock parts dumped into containers. I was going through and picking stuff out of each of the bins. Afterwards with my box of Treasures I negotiated a price and was pleased to have picked up this little guy.
I've not seen another Driver with a machine thread out the bottom. Was this something someone added so he would stay in his seat, or where earlier ones made this way ? Let me know what you think.