Swinden Key construction?
If the blades are tight (no excessive slop) get the cover material of choice, some epoxy glue, and install the covers. (Cut to length, install, use clamps to hold the covers in place while the glue dries) then shape after the glue is dry is how I'd do it.)
Forget about taking the knife apart and cover pins, unless you can get the measurements exact for where those holes goes, and can install them from the blade well.
Epoxy glue will hold a long time. That is what the factory used when they glued covers on.
As others have stated, Imperial-Schrade USA and all related brands ECXEPT Camillus shut down in 2004. (Camillus shut down in 2007.)
At the bankruptcy auction, Taylor Cutlery bought all the the names, (including those that were out of production for decades, such as Ulster, Hammer Brand, and NYKC) and all the intilectual properties.
Taylor contracted manufacturing to China, tho there were some contracted knives made in the USA. commemorative NewYork Knife Company BSA Scout knife was one.
In 2017, Taylor sold out to BTI, the current owner of all the Imperial Schrade brands.
Most are still made offshore, but there is a new "Heritage" line made in the USA. I don't know who is making them for BTI. Bear and Son, maybe?
Taylor did make some changes to the offshore knives comparred to the (now old) made in USA knives. Color differences in the Delrin, and a coarser "saw cut" on the Delrin, to help prevent the offshore knives from being sold as USA production.
No "Schrade+" on the blades, either, possibly to prevent a offshore blde being transplanted to a worn out USA handle knife"?
BTI has not undone the anti-fraud changes.
Since Taylor Schrade owned the names and intilectual properties, they could and did use the old Schrade, Imperial, Old Timer, and Uncle Henry names and numbers on the knives. BTI still does.
Taylor dropped the Swinden Key. (an improvement, IMHO)
BTI has not (to date) brought it back.
ALL offshore Taylor and BTI Imperial Schrade have stainless steel blades. Imperial is 3CR whatever MoV. Schrade, Old Timer, and Uncle Henry are 7Cr15MoV. The Old Timer "OTB" knives get 9CR18MoV blades.
I don't kow if the "Heritage" line has stainless steel (440A like Schrade USA used?) or 10xx carbon steel blades.
The offshore knives have a good heat treat. At least the Old Tmer and Uncle Henry do.
I have not tried an "Imperial" or "Schrade" branded offshore knife, so cannot say anything on them.
My guess is they have a proper heat treat as well.