The LM-221A slide rule is intended for use in interpretation of Aerial Photographs.

Procurement documents should specify the following:

a. Title, number, and date of this specification.

b. Quantity required.

c. Stock number.

d. Slide rule instructions required, unless otherwise specified (see 3.10).

e. Level of preservation and packaging and level of packing required (see 5.1 and 5.2). Level B preservation, packaging, and packing is intended to provide economical but limited protection, and should be specified only when it is determined the slide rules will be held in covered storage.

The margin of this specification is marked with asterisks to indicate where changes (additions, modifications, corrections, deletions) from the previous issue were made. This was done as a convenience only and the Government assumes no liability whatsoever for any inaccuracies in these notations. Bidders and contractors are cautioned to evaluate the requirements of this document based on the entire content irrespective of the marginal notations and relationship to the last previous issue.