I have two, I made both from farriers rasps one I ground and polished flat the other I left with the file side as is. They both work well but I prefer the polished one.
My collection L-R, 1st is a flipper made out of an old file (not by me), 2nd & 3rd are blue point slappers - the blue one weighs a ton, 4th & 5th are sykes pickevant spoony type whackers which come in useful in tight spaces that have been caved in.
Bashing metal about. The lighter flavours are used in a similar way to a planishing hammer but the very large contact area means less chance of stretching or marking things- great for knocking over flanges, planishing large low crown areas/gentle shape changes and the like. As they get heavier they become more traditional body spoons which are closer to 'dollies with handles' than hammers
Mine are all pretty much the same curviture, just smaller and bigger
I have just bought a job lot of panel beating tools from ebay. I plan to take out the ones that I want (and made the purchase for) and sell on the rest. I have two SP type slappers, file type faces with red handles. I also have slappers similar to the second and third from the left in Inchpincher's photo. The one similar to the one second from the left is a fantastic tool. I have just spent the afternoon dressing down some high spots on a wing. Love it. The other one is very heavy. I'm sure I'll find a use for it in the fullness of time (spring hammering?) However I'd recommend the one I've referred to for planishing.