I posted last night on the Clay Forum asking about finding the make and model of my Belgian O/U I purchased from a gun store in Texas. I had been shopping for at least a year and stubbled on this gun. I originally thought I had a Liege because the serial # started with L13 when I was on the Browning site last night. So after seeing your post this evening, I went to the website and discovered that I purchased an Citori Upland Special 12 Ga. It is in very good shape (95%) and the price was right. Condition which includes the amount of original finish and original configuration will determine value. You can also do your own investigation by looking at other models being sold that are in the same condition as yours.Try the or a periodical called "The Gun List" You can also reference the Blue Book of Gun Values which can be purchased on line at various retailers, however it takes some skill and experience to estimate percentages of finishes when using the Blue Book.
John Browning had envisioned it as the last gun the government would ban from private ownership and was designed to be the first over under shotgun that was affordable to the general population.
Actually, the Nomad was introduced along with the Challenger and Medalist in 1962.
Your pistol was made in 1966 which is denoted by the 6 after the p in the serial number.
The serial number, according to browning, means that it was made sometime between 19.
The 153 denotes the Hunting model Grade l with a 3" chamber. \n These were versions of the Winchester 101 as made for Sears.
Your model is a Citori 12ga 3" Grade I, made in 1985.