Shimano derailleur = 1985
Huret derailleur = 1984
To be specific...
3234956 is the sequential serial number. Check under/around the black cable under the BB for a stamped serial number. In general, but not always with Peugeots the number following the letter, Y3, refers to the year the frame was manufactured. Your frame was manufactured in 1983 for the 1984 model run.
Model is a P18T 'T' refers to the flat stlye handlebar. The same bike with drop bar would be a P18C where the 'C' designates a drop bar. '53' is the size in CM.