Meter chart envelope

Claim 1

An elongated rectangular envelope for containing and locking therein a circular sheet member, said envelope comprising a front panel; a back panel, said back panel including a top edge portion and a pair of spaced apart, generally triangular cut portions extending downwardly from said top edge portion, said cut portions being disposed in mirror image relationship to one another; a pair of spaced apart, opposed side edges, said side edges defining the length of the envelope; a closed bottom edge portion, said bottom edge portion defining the width of said envelope; a top cover flap hingedly connected to said front panel along a first fold line; and a generally rectangular locking flap hingedly connected to said back panel along a second fold line defining its bottom edge, opposed side edges of said locking flap being disposed between said cut portions and substantially centered between said side edges, said locking flap including a terminal top edge substantially parallel to and colinear with the top edge portion of said back panel, the width of said envelope and the distance between said second fold line and said bottom edge substantially defining a square area such that when a circular sheet member is contained within the envelope, said locking flap may be folded into the envelope such that the sheet member is sandwiched between said back panel and said locking flap so as to minimize slippage of the sheet member within the envelope.