Diatomaceous earth is the best 'organic cure' for smells in trunks .
One of the problems with molds/mildews/fungus/rot is that it has a microscopic structure , which can even penetrate into wood .
With metal-clad trunks , this means that the micro-critters can be encapsulated in the happy & dark space between the tin & wood , which makes abatement problematic , time-consuming & adds a bit of labor/supplies to the project .
More or less , the abatement is a 'fumigation' process which requires the trunk being sealed-up inside of large plasic bags (preferably outside) for a day or so , while the volitile/aromatic chemicals do their work .
As wendy177 stated , mucelage glue (& fabrics/papers) is also an issue , and very small insects too .
I'm guessing that you're planning on putting a finish on the interior of your trunk ; if you do , you can add a fungicide to the water/acrylic-based paint/varnish you use , which is a long-term prophylaxis .
The big deal here , besides doing micro-genocide , is to fully dry out your trunk before (& after) finishing its' interior .... this process can be aided (on the cheap) by using a small heat source , like a 40watt light bulb in a safe light fixture (no plastic drop-lights) , inside of the trunk - this will cause some odors , so again , do it in a well-vented space .
Some restoration specialists use a UV lamp , closed up in the trunk , to kill microbes (prior to finishing) .
Bottom line is that these types of items are usually closed-up (dark,damp&stagnant) for most of the time ....living in the NW , you know how this feels...
I keep a small sachet of cedar shavings , with a drop or two of food-grade cinnamon oil , inside of closed-up trunks like these (usually inside of an old cotton sock) , with another small bag of diatomaceous earth .