It's a good substitute. India ink is put into the scratches to highlight the etching. Some of the art is utilitarian. He has a line of knife handles made from micarta which cruising yachtspeople buy. You pay for the labour and name of the artist.
Many pieces end up as displays on the cabin bulkhead or over the fireplace back home.
Certain original scrimshaw pieces made by seafarers during the last century are now collector's items. Value increases with the artist's name and that of the ship. These were gifts made of seashells inlaid in a small box. Some of the seafarers bought their valentines from handicraft shops on Caribbean islands before they hoisted sail for their homeport. This wasn't done to pull a fast one and pass off the handiwork as their own work, but simply to save time.