Kraus use several markings which allows them to be recognised.
Often there will be a collation of the manuscript on the back pastedown, folowed by initials, "p[ro] HPK" and a date. For many years the collations of manuscripts were done by J. S. Kebabian. In this case the collation was done by JSK p(ro) HPK in June 1976:
Usually there will be a stock/inventory number in the lower right corner, underlined, and below this a price-code. Usually the price-code has been erased. A stock-number beginning with a "P" indicates that this is one of the Phillipps-Robinson manuscripts (for more examples, see the Robinson page). Over 100 of the Phillipps-Robinson-Kraus manuscripts were offered in Kraus catalogue 153 (1979); others remained in stock until the business closed down.
Here "A/I/2" is the Kraus shelfmark (the gu/- is Thorpe's price-code, the 25,000 is unidentified, but looks recent).
In this image the "C/VI/8" is a Kraus shelfmark, of a type which typically appears, as here, in the upper left corner of the upper pastedown or first flyleaf. Especially valuable manuscripts have "Safe" and a number instead of a three-part shelfmark: