My P-series casserole was made in 1971 or earlier.
After a dozen years or so of Corningware making their classic Blue Cornflower, the decided to try a few new designs. Floral Bouquet was first offered in late 1969 with limited promotional pieces, all with a wrap-around design -- the only wrap-around pattern Corningware ever made.
By 1971, Floral Bouquet was released as a full line, with 2 variations of the wrap-around pattern. In 1971 a simplified sides-only pattern was introduced with the same Floral Bouquet name, and for a brief time some casserole sizes were available in both wrap-around and sides-only patterns.
From 1972 onwards, only the simplified pattern was in production, along with the updated casserole shape.
Here's my casserole again:
Original P-series shape produced until 1971, with the transitional sides-only pattern produced from 1971 onwards. Therefore, my 1.5 quart casserole is from 1971 and celebrating it's 40th birthday!
Sadly, this casserole was lid-less, an occurrence that's pretty common. I suspect that lids were more likely to break than the Pyroceram material of the casseroles themselves. I now have 3 casseroles of this size, and only 1 lid between them (and it's a post 1972 lid at that! I found it in a bin of lonely lids at a thrift store for $1)
The Complete Guide to Corning Ware & Vision Cookware by Kyle Coroneos