This is an Anchor Hocking Co. Fire King blue sapphire “Philbe” thin wall D-handle mug. This pattern was produced from 1941 until 1956.
This mug is a real treasure! First of all it is Philbe, which is one of Fire king’s most beautifully intricate patterns, and also because it is a thin-wall mug. Most of these mugs are 1/4″ thick, and they are nice, however, this one is just more delicate, and feels nicer in your hand.
This mug is in excellent condition. It does have two tiny imperfections, called straw marks, in the glass. They are not breaks. This happened from time to time during this time period, due to a more primitive manufacturing process.
Take a look at the pictures, and if you have questions, please e-mail.