Hi Gill. Checkering as you have found out is the one area where the use of steam on dents more often than not does not work, possibly because the wood fibres are cut many times in such a small area by the checkering process that the steam cant be driven into the wood to swell the damaged fibres. Though there is a way of repairing checkering but in many cases it is not worth the effort unless it is a very high value gun. It is done by cutting out the damaged area down to about 1/16 of an inch if you can the deeper the area is made the more successful the transplant will be, with the removal cuts being done along the bottom of the existing checkering lines (a medical scalpel works well because it has a fine blade). The cut out area usually ends up in a diamond shape where you can transplant a small piece of wood the same shape using a top quality Adhesive, now you can harvest slivers of wood from under the forend Iron and from under the trigger guard strap if the timber has to match exactly. If a close colour match is not really necessary just use any piece of walnut and stain it to match as near as possible after you re cut the checkering using a triangular needle file rather than a checkering tool and if done well the repair is invisible. This type of work is not for the feint hearted and needs to be practiced before you let yourself loose on an expensive gun!!

The only lessons in my life I truly did learn from where the ones I paid for!