Brandon, You are correct that the grips are different shapes.
German manufactured Lugers and early Swiss have the wider grips and later Swiss, 1929 I believe, are sleeker, as you state. Here's links to Simpson's to show the difference.
http://www.simpsonltd.com/product_in...oducts_id=2408
http://www.simpsonltd.com/product_in...oducts_id=4865
http://www.simpsonltd.com/product_in...oducts_id=2427