Excellent job photographing your rifle! The details are good for helping in the attempt to identify the action. I cropped and lightened this last one:
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Originally, the Siamese Mausers had dust covers on the actions which could be slid from front to back:
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Note the presence of the Chrysanthemum crest on the front ring. Far too many Siamese Mausers were 'sanitized' by sanding off the markings and used for making .45-70 rifles. This was touted as being an amateur project for which we now have literally hundred of unfinished attempts relegated to some closet or basement as failures. You are lucky yours feeds at all.
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Note the two oval indentions on the action which are the stop points for the dust cover.
Also note this marking as seen on your action (not the numbers...):
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Your action has been modified and highly polished which does more damage to identification than almost any except machining.
Personally I would remove the barreled action from the stock and look for proof marks on the bottom of the action. You can also remove the scope mounts to check both the front and rear action rings. There are volumes written on the various models of Siamese Mausers so I won't try to accomplish everything on your rifle in one short post.
Best of Luck!