I'm not sure if there were ever formal pitch markings, as it's a floodplain meadow and a lot of that would just end up lost historically. The fields were also used for a wide variety of sports, so I think the bounds were mostly set up and taken down as needed. To wit: home grounds for a local hockey team going back a century or so; various different athletic events at Sports Days at Albert Road School; club practices. As I remember we put down those little plastic semi-cones as markers.

Albert Road School shut down in 2008, so that's the time period since it's been in active use I think. Ramsey AFC are currently trying to secure the use of the site, though having a tough time of it:

https://www.manxradio.com/news/isle-of-man-news/desc-ignoring-ramsey-commissioners-over-football-clubs-wish-to-use-empty-fields/

https://manx.news/inquiry-hears-evidence-for-the-future-of-leisure-facilities-in-the-north/

Personally I'd leave the pitch markings until we know more, since fundamentally the site is a sports grounds.