Up for consideration is the Antique Pyrex Primary Blue small mixing bowl. This bowl has NO numbers stating that it is a #401 bowl or 1.5 pint in size. Also, the thickness of the material is noticeable thicker than the other primary blue bowls that I own. Wonderful luster on this little guy! Scratches can be seen in the photos. Very minimal utensil markings on the inside.
The bottom reads as follows: T.M. REG. (Arched upwards) PYREX U.S. PAT. OFF. ( Arched downward)
This is a great piece, still has a lot of years left in it!
Please feel free to ask any questions or request further photos.