(e) The sling cord attached to eyes in the frame by means of brass snaps with black burned finish shall be round and braided from four strands of pliable tan leather, and shall have a diameter of at least one-eighth of an inch and not over one-sixth of an inch.
(f) The case and strap must be exactly like sample, and of No. 1 stock. Care must be taken to put in only compasses that are in perfect condition. The strap buckle must be of brass. The glass, when closed, must not exceed 4 inches in length, and the glass, case, cord, and strap, complete, must not exceed 25 ounces in weight.
(g) The frame shall be constructed with jointed bars for interpupillary adjustment.
5. Service field glass, type B.—(a) The requirements of part 4, service field glass, type A, of this specification, shall be followed in the design and construction of the type B glass in so far as applicable.
(b) Power: The lower power shall be approximately 4½ and the high 6½ diameters.
(c) Object lenses: These shall have a clear aperture of at least 1¾ inches diameter.
(d) Case: Case and carrying strap shall be furnished as required in part 4 of this specification.
(e) This glass shall be constructed with jointed bars for interpupillary adjustment.
(f) The sunshade, when drawn out, shall project not less than three-eighths of an inch and not more than 1 inch beyond the edge of the cell.