Sheet increment sign assembly

Claim 1

IN A SHEET INCREMENT SIGN ASSEMBLY HAVING A PLURALITY OF RECTANGULAR PANELS ABUTTED EDGE-TO-EDGE TO FORM AN INDICIA-BEARING FRONT FACE, A DEVICE OF THE CHARACTER DESCRIBED FOR HOLDING THE ABUTTING EDGES OF SAID PANELS IN ALIGNMENT WITH EACH OTHER COMPRISING IN COMBINATION: ELONGATED SEAM-LOCKING STRIPS RIGIDLY MOUNTED ON THE BACK SIDE OF EACH OF SAID PANELS ALONG ABUTTING EDGES THEREOF BUT WITHIN THE MARGINS OF SAID PANELS, EACH OF SAID SEAM-LOCKING STRIPS HAVING A BASE PORTION ALONG ITS EDGE REMOTE FROM THE EDGE OF THE PANEL, SAID STRIP BEING RIGIDLY SECURED ALONG SAID BASE PORTION TO SAID PANEL, EACH SAID SEAM-LOCKING STRIPS HAVING A RETAINING PORTION ALONG ITS OTHER EDGE OFF-SET REARWARDLY FROM SAID PANEL AND EXTENDING PARALLEL TO THE PLANE OF THE PANEL, SAID RETAINING PORTION AND PANEL FORMING BETWEEN THEM AN ELONGATED RECESS OPENING TOWARD, AND EXTENDING PARALLEL TO, THE ABUTTING EDGE OF SAID PANEL, AND AN ELONGATED LOCKING ELEMENT HAVING FLAT LOCKING PORTIONS SLIDABLY DISPOSED WITHIN SAID RECESS FORMED BY A PAIR OF SAID SEAM-LOCKING STRIPS ON ADJACENT PANELS IN ORDER TO INTERCONNECT THE ABUTTING EDGES OF SAID ADJACENT PANELS, SAID ELONGATED SEAM-LOCKING STRIPS AND LOCKING ELEMENT EACH BEING CONTINUOUS AND EXTENDING SUBSTANTIALLY THE FULL LENGTH OF THE SEAM BETWEEN SAID ADJACENT PANELS, THE THICKNESS OF THE LOCKING PORTIONS OF SAID LOCKING ELEMENT BEING ONLY SLIGHTLY LESS THAN THE WIDTH OF SAID RECESSES MEASURED PERPENDICULAR TO THE PLANE OF SAID PANELS SO THAT SAID LOCKING ELEMENT AND SAID PAIR OF SEAM-LOCKING STRIPS COOPERATE TO LOCK THE ABUTTING EDGES OF SAID PANELS SUBSTANTIALLY IN ALIGNMENT WITH EACH OTHER.