Once you remove the moldings and pane, look for a number or other type
identifying letters/numbers/code somewhere along the jams. If you
know who made the window, that code or number is used to make an
identical window, pane, moldings... whatever needs to be replaced.
On double hung sashes, casement windows, etc., the numbers are
"tattooed" on the edges of the sashes (usually the side edge), as well
as either on the jam and/or on the outside of the unit's frame.
This identifying of window units is standard for the major companies
like Pella, Jelwen, Kolbe, etc. and identifying a unit is essential
for a particular product/unit under warranty.
If your window is not too old, it may still be under warranty.
Kolbe's warranties used to be transferable to new home owners, when a
home would be sold... the units were warrantied, no matter who the
homeowner was. I'm not up to date to know if Kolbe's warranties are
still that way.... and I've never known about Pella's or Jelwen's
owner-transfer policies, at all.