I just checked in "Goin's Encyclopedia of Cutlery Markings", and "Levine's Guide to Knives and their Values" and there is no mention of an LBK Co. These books usually have a lot of retailer's names besides manufacturer's names but show nothing for these letters. Appears to be around 1900 by style, could well be a German import, they made thousands, many maker's names lost to time. Were it an American maker it would likely be in those reference books.
I did look up IBK also with no results.