I think the Blues Harp is almost identical, and I have never noticed any difference between that and the Marine Band myself.

The main difference seems to be that nowadays they are all made from plastic, not wood. This does have advantages, but also disadvantages. Soaking the wooden ones used to improve the sound, I suppose because the wood swelling up made the seal tighter. Doesn't work with plastic!

Also, the key is printed on the side, not embossed in the metal, and soon rubs off!

When I started buying them, they cost 10/6d.