Need help with some antique style windows

A landlord from Georgia says:
Hello - hoping you may have a solution.

I have several wooden double hung windows (single pane) in a historic building in Savannah GA. They currently can open but have absolutely no ballast or chain or anything so only stay open when putting a something under the sash to hold it up then they slam down of course when the wood or whatever is taken out.

This is for a small bed and breakfast so hoping to be able to allow guests to open windows and get some fresh air.
Do you have anything that could work? Maybe some sort of surface mounted ballast system?
Someone mentioned a "steam punk" style crank system they had seen before.

Thank you for any help!
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Paul from SWISCO responded:

Many thanks for posting. We believe your wood sashes have routed channels along the sides of the sashes. Look down on top of the sash ends and see if they have a open channel. If so, we have a balance system that wood window manufacturers used back in the 1940's: our Series 500 balances. We will need the the height of each wooden sash, as well as the glass height of the top and bottom sashes including the wood mullions in the measurements. We will figure the balance tube lengths from there.

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