Antique BONE ENGINEERS SLIDE RULE So Rare! UNIDENTIFIED + Letter from V.P of K+E

ITEM DESCRIPTION: Being offered for sale is the EXTREMELY RARE, UNIDENTIFIED & UNUSUAL antique BONE SLIDE RULE + SIGNED LETTER (and original stamped mailing envelope - see last 2 pic) from the V.P. (at the time) of Keuffel & Esser (responding to the original owner's query about the slide rule - in which he admits he does not know and will have his slide-rule experts look into it (and an answer was never found)) from circa the mid -to- late 19th or possibly very early 20th century (best guess), as seen in the pictures/as described in the title. PLEASE SEE BELOW FOR IMPORTANT CONDITION NOTES. Being offered for sale AS-FOUND, uncleaned. May require a thorough detailing to bring to its full potential. SATISFACTION GUARANTEED or your money back...no questions asked!   CONDITION NOTES: * VERY MINOR OVERALL WEAR BUT REALLY IN GREAT SHAPE, IN OUR HUMBLE OPINION. * VERY LIGHT BOW/SLIGHT ARC TO BOTH SIDE'S INNER/SLIDE PIECES. * WE SEE NO BREAKS OR REPAIRS. * APPEARS TO BE A FULLY FUNCTIO