Chain-motor cable question

Does anyone know what that silver pin on the female end of 50 amp cable that feeds into an 8-way distro is? I don't remember if this is the right one but it looks like this: http://www.hubbellcatalog.com/wiring/datasheet.asp?PN=CS8369 Someone opened one up for me and told me it was the ground since the green wire was in the center. Not sure he's right since the specs say the ground is the copper strip on the side of the connector. Thank you.

It is my understanding that the center pin is common/neutral and the outside strip is ground.

That was my first guess. But it seems weird to have a neutral connection when 3-phase motors don't need/use a neutral and that it's a male terminal on a connector that's female. But I don't know what other uses this connector has or if it's used with single phase power.

That is commonly called a California connector. It can be wired in multiple ways depending on how the "tits" on the connector align. Commonly used to tie distros to smaller distros such as amp racks and motor drives. That center pin IS NOT a current carrying conductor.

All the different flavors:
http://lockingpowercords.com/category/31-hubbell-50a-twist-lock.aspx

https://www.controlbooth.com/threads/california-plug.23409/page-2

http://www.cooperindustries.com/con...king50A_Non-NEMA_CAStandardNylonSpecSheet.pdf

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https://www.controlbooth.com/threads/california-plug.23409/page-2
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Specifically, https://www.controlbooth.com/threads/california-plug.23409/page-2#post-207542 .
Also at the wiki entry for California plug.

Thank you. I wish I knew how to tag you. It's something that has always puzzled me.