the bottom of my Bachmann spectrum mogul engine that is! 
Is it some sort of fixture for display, or does it stop the wheels coming off on sharp curves or...?
Because it's always been either pitch black or raiining hard when I've been home over the last week or so I've not been able to run it since it's purchase otherwise I would have just tried it out...but I'm interested to know what it's for.
One of the screws is missing from the centre and it means the device can spin round...probably not good...
Is it some sort of fixture for display, or does it stop the wheels coming off on sharp curves or...?

Because it's always been either pitch black or raiining hard when I've been home over the last week or so I've not been able to run it since it's purchase otherwise I would have just tried it out...but I'm interested to know what it's for.
One of the screws is missing from the centre and it means the device can spin round...probably not good...