One of the biggest problem with older calls is the build up of chalk on the lids, most folks used what ever chalk they had for chalking their calls and a lot of it was a wax based chalk. Take the call apart. You'll need 2 grits of sand paper or sanding sponge, like a 180-150 grit and a 100-80 grit. Look at the bottom of the lid and see where the angel wings are on the lid ----) from where the lid rubs on the rails. Mark that area from the back of the angel wing to the start of them, should be about 1-1/2" area, with a pencil. Lightly sand the lid the lenght of the lid with the finer grit, very lightly your not sanding the wood off only the chalk, to get back to the raw wood. Then cut a stip of sandpaper about 2" wide, and get someone to hold the lid for you. Go to the area you marked where the angel wing were, and hold your sandpaper at the ends and let it form around the crest in the lid, and draw it back and forth acrossed the lid a few times to rough that area up with your rougher grit paper, you want it rough it's a friction call. Again very lightly, just enough to rough it up, not to sand any wood away. Take your sanding sponge and just set it on the rails, draw it from the back of the call to the screw, only one way lightly. Put the call back together with the lid level or a bit high at the screw, looking from the side of the call, and play it, without any chalk, and adjust the screw to get the sound you want, then add your chalk and it should be ready to go. Chalk build up on the lid and rails and glazing from playing, is what kills the sound in box calls. It's a friction call and it has to rub wood on wood to sound right, chalk makes it easier to play if it's not to much chalk. That way you get the sound of the wood it's made from, not the sound of the chalk used to play it.
WI Youth & LTH Mentor
Dodge Co. NWTF