Your Rifle was issued to the Western Australian cadet corps .Fairly hard to find in Australia ,most are Victorian of NSW issue.The trigger safety is a Sportco addition ,Martini Cadet rifles had no safety .They had a cocking indicator than moved up between the breech block and the action frame on the right had side .The martini is a very strong action tested by white labs in the US to 60,000 psi.However the extractor is its weakest feature ,so you need to be mindfull when handloading for it .Sportco company hasnt been operating for a very long time ,but many of thier conversions are still prevelent here in Australia.They converted thousands of Cadet rifles to 22RF , 22RFMag,22hornet , 222 Rimmed ,and many other calibers ,also they converted thousands of surplus Lee Enfields to 303/22 ,303-25 , 303-270 , 22 Hornet and a list of other calibers too long to mention .I love the small frame martini and have quite a few in my safe.I would hazard a guess that your rifle was rebarreled/ rechamberd in the US ,the forend hanger is not of the Sportco type. The action internals are fixed into the frame with a spring pin at the lower front of the frame , knock it out and with the cocking lever pull down at the front the guts will come out in one assembly .To drill a hole in the rear of the action ,the barrel will need to be removed and a threaded drill guide screwed into the barrel recess and the apropriate sized drill used to drill the hole for cleaning rod acess from the rear .The action internals will need to be removed to clean from the rear .