These two insulators have not appeared in any insulator reference book that I know of, so I decided to do this article. Information included is based solely on the two insulators in my collection, so note differences to the machine drawings in Milholland's books. Because of their size and weight I am unable to display them, and they are in constant storage; so being able to share them with you is indeed a pleasure.

PYREX 553

CD #328, 18-1/2 pounds, 4 part mold, smooth base, clear 1-3/8" peg opening, 8-3/8" high, 12" diameter (across) Embossed on skirt from underside reading out: "PYREX T.M. REG. U.S. PAT. OFF. MADE IN U.S.A. 553" centered at one mold line. Some really beautiful air bubbles!

PYREX 663

CD #330, 27-1/2 pounds, 4 part mold, smooth base, yellow straw (Because of glass thickness, glass appears clear at thinner sections.) 

2-1/4" peg opening, 11-1/4" high, 15-1/8" across. Embossed on skirt from underside reading out, except the A (embossed on outside of skirt): "PYREX T.M. REG. U.S. PAT. OFF. MADE IN U.S.A. 663 - A" placed without reference to mold lines. Embossed at crown top "A". A most fascinating Pyrex insulator!