Probably from the 20s or before.  I kind of collect old doors apparently.  These I use to make items out of as I have shown in the pictures.  There are 2 of these.  They measure 39 X 9.  One has a slight buckle/warp. Both have layers of old chippy paint.  you can either incorporate it or sand it off.    Buckle/warp is in picture 4 I believe and not that noticeable but it is there. Deducted a few dollars off this one because of the buckle.   I have other door inserts up for sale as I will never finish all of them.  I would be more than happy to combine shipping.  Shipping is high because of the size.  thank you  8