the turks have always taken a casual approach to labeling and documentation of firearms changes and maintenance.

they work or you fix them , the idea of replacing things on a schedule seems to have historically eluded them or having parts that hold a standard , back to if it works send it.

some importers hold them to a better standard and QA

Find the country code stamping on the barrel that could narrow it down.

Wasn’t there a company called Hastings that made aftermarket shotgun barrels?

To the best of my knowledge Remington never made a 1100 or 1187 barrel with a plated extension. Most barrel locking lug cuts will probably look similar due to using a similar locking lug type. And if there are no markings on the barrel for manufacture or proof mark it might just have been "borrowed" without going through the required formalities. I've never seen a barrel without at least shell length roll marked on it.