| 摘要 |
<p>749,169. Glass. PITTSBURGH PLATE GLASS CO. Oct. 18, 1954 [Feb. 11, 1954], No. 29899/54. Addition to 739,341. Class 56 A minor element is formed and fused in a ground and polished countersink 5 in the major element 4'of a bifocal lens blank by flowing molten glass G of the required refractive index into the countersink.</p> |
