Fulton-

I'm not suggesting the rifle is rusted shut.
I am however noting that since the rifle was likely campaigned in India, the works of the locks, safety system, triggers, cocking system etc may well have been affected by the humid climate.

I do not know perfectly well the patent design of that hammerless backaction sidelock Lever Over Guard double rifle action.

The properly qualified gunbuilder will.
This may simply be a case for penetrating oil.
It is also possible you could end up screwing your stock up by getting that penetrating oil into the head of your stock.

Does the safety selector switch work?
Are you able to remove the forend?
Do you know for double damn sure that there are not cartridges in the chambers?
Are you sure of that?
Consider the possibility that some dude put a pair of fired cases in the chambers, snapped the strikers to relieve the springs, then left it that way - and since then the brass has somehow corroded, swelled, and stuck in your chambers - sticking the gun shut.

You got a cleaning rod that's longer than those barrels?
Drop it down the muzzles and see if it makes it's way down to the breechface. If it does, grab your laser pointer and shine it down those bores and take a peek.
Are you looking at your standing breech and strikers or are you looking into the bellies of some spent brass?

That's just a thought.
Could be anything really.

I'll say it again though - send it to JJ at Champlin Arms and get it over with.
The cost of replacing or repairing parts damaged or broken along the road to discovery could pretty much leave you with no residual value in the rifle.
A checkup at JJ's won't cost much, a phone call to him will cost nothing.

--Tinker