Funny all the Izzy ones I have have German locking collars.
....and they may well have, remember the Israeli's replaced either part as needed. If the locking collar extensions have identifiable WW II German markings (known mfg'r codes, WAa's, inspector markings, Adlerampts, etc.) you're fine. It is only the Israeli MADE extensions that are suspect. The presence of the IDF ownership marking, the stamp that looks like a Star of David (but is actually not) alone is not proof either way. The presence of ONLY this marking MAY be an indication of Israeli mfgr. Best way to ID them conclusively is by the metallurgical description. The German, or Yugo, metallurgy is visually way different. Take a known, good condition, German one for comparison.
The other way to conclusively proove it (was) an Israeli-made, problem and suspect, extension is to shoot it.....if it shatters in your face and damages the gun (only, if you are lucky), well, you just prooved it was one of the bad ones!! ':lol:'
The best way to handle these is to immediately exchange any collar found on an IDF BBL that is not CLEARLY identifiable as WW II German or Yugo Post-war by the presence of the known extensive markings usually found.