Here's a picture of my M40 where you can see the hump is not on the same plane as the stock. This was a repro stock that began as (IIRC) a Rem Police stock.
The second picture is another M40 with (IIRC) a real M40 stock where you can see the hump extends higher and is almost even with the stock.
Not saying yours are real or not as there are other indicators.