PRS SE Custom models were made Korea up until 2019 when production of some SE Custom models was transferred to Cor-Tek Indonesia (Cort). Date of manufacture should reveal where yours was built.
I don't own a PRS so don't know if they have the origin stamped on the reverse side of the headstock or on a sticker on the reverse of the headstock as is common practice. Edit: the 2021 MII model does, belatedly sighted and confirmed in the vid linked in the final paragraph. If not indicated on the manufacturers (shipping) box label assuing you might still have it somewhere, there may even be a serial number legend online someone in a PRS fan forum can point you to which reveals DOM & POM info. [br][br]Regardless the build quality and segment step above the SE Standard, the Custom is still a part of PRS' budget line. Can't confirm definitively, but pretty sure neither Cort Korea nor Indonesia would be using a nitrocellulose finish on anything. It's a safe bet that if a manufacturer doesn't mention the finish material specifically as a feature, and here PRS don't, you can bet your life it's a contemporary polyurethane finish.[br][br]My own guitars spend their life on Hercules wall hangers when not on a floor stand. All polyurethane finished necks, satin and gloss. 4+ years on, no sign of reactive issues, nor would I expect there to be. However ....[br][br]N.B. FWIW I've read the same 'reactive with nitro finishes over time' complaint about the protective foam rubber compound material Hercules use on their guitar floor stands. [u]Hercules now include a warning note disclamer inside the box[/u] with those stands, (I know as I very recently bought two of them) so it would appear Hercules acknowledge the potential for reaction with their rubber bumper compound as = true. [br][br]The Hercules wall hangers I have (GSP38WB) deploy a visually similar compound on their retaining arms and back bumper which given the note now included with their floorstands suggests to me it would be unwise to use them for any guitar with a nitro finished neck. I've owned my Herc wall hangers now for over 4 years, but at the time they were purchased, there was no warning note included in any of their boxes.[br][br]P.S. Watch this 08/2021 vid. Shane demos the 2021 SE Custom 24 (on loan) here which he confirms is Made in Indonesia, but mentions, paraphrasing, he 'owns its Made in Korea SE Custom 24 predecessor and will offer a difference comparative later' in the vid. The 2021 version in this demo is obviously Polyurethane finished to my eyes.