Oporto Bottled means what it says - up to the mid 70's it was permissible to ship Vintage Port in casks to be bottled by wine merchants. This is no longer allowed and all port is now "Oporto Bottled".
"Top Shoulder" is referring to the level of wine in the bottle - known as the "ullage". On older bottles the wine level can drop due to evaporation or leakage. The shoulder of the bottle is the curved section between the main cylinder and the neck. "Top Shoulder" therefore indicates that the wine level is just below the base of the neck.
Personally, I don't think this is a good sign for a 1970 bottle that has been properly stored.
NO VINTAGE PORT that is younger than bottles from the 1940s, should be into the shoulder when purchased. I have bottles from the '20s and '30s that are still into the neck.
Provenance is EVERYTHING. Be willing to pay for it now, or you most certainly will pay for it later!