Again today going through of my older coins I found these two Franklin's Proof that were DDO's. 1954 see image of 4 as to pup. and the 1955 see image of 9 pup. 1954 Pr DDO-001 & 1955 Pr DDO-002
I don't know that I necessarily agree with your attribution unless doubling is present on other devices on the coin. The "4" on the 1954 appears to not actually be doubling as much as a die anomaly which only affected the 4 such as die wear. The "9" on the 1955 could very well be Class II (Distorted Hub Doubling) but its of an extremely minor nature. Just my opinions.
Have a look for your self Franklin lovers.com and yes there are other PUPs on both coins just didn't have the time to shoot them all and post both the 54 and 55 are spot on.
Were not a whole lot of early 50s Franklin proof halves struck. 300,000 more or less each year? I'm thinking maybe 10 dies or so which should make these varieties fairly common among proof halves.
Its not a valuable one but it is a low population on pcgs that ive noticed and yes 233300 minted in 1954
I should not have described the varieties as common but instead described them as highly prevalent among that year's proof half coinage. Probably something like 1 out of every 10 coins.