Ron,
I think this side plate might be from a M1906/24 Bern luger...the variety that came around serial # 27xxx...with the "island" of the side plate running to the top of the side plate.
It has more metal visible above the take-down lever. I think the M1929 side plate has less metal that would not be visible behind the take-down lever.
See attached photo :
Photo from Gun Broker :
