I doubt that a HBH would be original equipment on a .32-20 M&P. Production stopped on those around 1929-30, but they were still cataloged and sold by S&W for the next 10 years. My guess would be that a HBH would be a later addition, but nonetheless the hammer itself is very desirable. I think that there was a recent posting indicating they are going for about $150 but I have no idea if that is correct.