Lovely watch Kathy. Congrats! Indeed an early MP case again. They are easy to recognise since the engraving on the side typically is different from the engraving at top and bottom. American Standard initially did not master the technology to attach stones, but very quickly they could, meaning they also started producing this model. It got a name then in December 1924, called Duchess. The AS case can be recognised by the number of holes in the wings. Two in the case of MP and 4 in the case of AS. Also the engraving is now the regular Laurel leaf engraving all around the bezel. The 5 K was an eBauche from Glycine from who Bulova shortly bought from 1923 until early 1924. The 1579 is the serial number. Highest I have ever seen is around 3500, meaning they did not buy many from them. Their main movement was the 5P, supplied by Aurore based in Villeret. More details in my book!