Antique Wood/Glass Wall Mount Swivel Minutes Timer from Silver's Brooklyn-Works!

Description

The timer is really something!  It has metal loops at the top and bottom for hanging and it doesn't even matter which end you have up.  There's a small knob at one end that you can use to swivel the timer 180 degrees to start the sand flowing from one end to the other.  Or you can just use your finger to swivel from down to up.
There are minute markings on each side of the timer glass, from 1 to 6 minutes.  The numbers and their underlines are stamped into the wood.  They were probably painted to start but when they got hard to see, someone painted over the original dark lines with a light color paint.
It's not easy to see but stamped into the wood at both top and bottom is: MINUTES.  Below that it says SILVER'S BROOKLYN in a smaller size.
On the back of the wood that attaches to the wall is stamped MADE IN GERMANY in even smaller letters.  On the back of the wood that holds the timer, the number 750 is stamped.
8 1/4" tall and 1 1/2" wide
I can't find any timers like this on line - if anyone knows how old it is, I'd be interested to know.
Your purchase supports the Port Jefferson Historical Society Consignment Shop - thank you!