Well, in the course of doing some maintenance on my Boler
17, I encountered the cabinet latches, which were brass and covered in green furry verdigris, looking very grotty and seized up solid. The plastic parts of the concealed latches were, of course, fine. However, to open the cabinet one inserts one's fingers under the round button holder and press the button in the center. The buttons wouldn't press as everything was seized up. A good, firm "whack" on the button opened the cabinet, but, of course, it wouldn't latch closed any more.
So, after some I-net research, I found the solution
Remove the verdigris-encrusted part and drop it into a container of vinegar and wait about a half-hour of so.
Pull the part out, rinse with water, brush with an old toothbrush, and replace in the vinegar. Repeat as required.
Allow to dry and oil the moving parts
By the way - DO NOT - EVER!!!
- use WD-40 as a lube. The "WD" stands for "water displacement". It is not a lube and in fact becomes sticky after a while. Use a light
machine oil instead!
Replace latch on the cabinet door.
Good as new!
(Of course a bit of sanding of the wood under the mounting spot to remove the "clag" on the wood before putting the latches back on helps too!)