If you remove the distributor cap ( either 2 clips or 2 screws) it should be marked on the cap between the plug (HT) terminals/sockets, assuming it's an original or main dealer supplied cap.
Iirc, Marelli distributors use a brick red colored cap, Ducellier use a black cap?
If you use a light and mirror (or one of those new-fangled inspection cameras) to get a look at the distributor body. Magnetti Marelli dist. bodies had the name cast into the body midway between the mounting and the distributor cap. It looks like a crest iirc oval? in shape.
Al.