Fundamentally there is no difference. Typically, neither has cocking indicators or the Doll's Head rib extensions that virtually all other Lefever sideplate guns have. It is believed that the I grade was produced to be marketed by independent firms while the DS was marketed primarily by Lefever Arms Co. through catalog sales.
It is believed that these guns were the first Lefevers to be produced prior to an order being placed. That is, made like most of todays guns to be placed for off the shelf sales. Higher grade Lefevers were generally made to the buyer's specifications as to stock dimensions, barrel length, choke, etc.
