This is a quick and easy way to install a flat comb in to a Marine Band harmonica. The stock comb has dimples to make room for the ends of the rivets which hold the reeds. My combs provide more surface area to make an airtight seal with the reed plates and the rivet ends need to be flattened.
This is a harp in the key of G. The end result is a fantastic harmonica that is loud and responsive. I was happy with the instrument but was not satisfied with the 4 overblow due to the shape of the reeds (out-of-the-box profiles).
I spent a few minutes and did some re-shaping of the blow and draw reeds to make them more efficient. It's much more work than just gapping. But the end-result is a 4 blow that is not tight and plays normally with hard pressure as well as a solid - and bendable - 4 overblow.