As most know, the large Military Alcohol stove will not accept the modern Trangia snuffer/flame adjuster cap without modifying the cap.
The solution is the Tatonka cap, which fits and works perfectly on the large Mil-type stoves.
Watch the Vid:
Here It is well-made of stainless steel. The bright/shiny exterior finish can be subdued using fine sandpaper or steel wool, if desired.
The cap (with shipping) is not as inexpensive as I would like, but if using it saves a hard-to-find military-size cap gasket from melting, then the Tatonka cap may be worth it. YMMV. The only source for these (at this writing) appears to be Amazon. If you can find a source with a lower overall price, please link it.
Swedish Military O-rings available
HereModern (new) clone of Stainless Steel version of Swedish Military stove
HereI know nothing (pro or con) about the Pathfinder alcohol stove offered as an option; The optional plastic cup looks a lot like the original Swedish Mil cup that came with the Mil cook sets and is available on eBay. It's shaped as it is for internal stowage within the stove, and it actually fits along with the large Mil-type burner, and the original fuel bottle, with a little room to spare.
History: Two versions of original Swedish army cook set, one aluminum, other stainless steel. Aluminum version is more common, so commands a lower relative price. Aluminum versions a bit lighter, but more easily damaged. After some looking on Ebay, it appears that there are folks posting outright fake/mismatched items, and perhaps some Red Chinese clones. Suggest before buying any milsurp Swedish cook set that you become familiar with the genuine item. Personally, I
might trust genuine Swedish metals (including aluminum), but I have severe reservations about ChiCom aluminum. YMMV.
Documentation
HereDisclaimer: No financial interest.