Public Service Announcement. I have two different A2S4000's in my possession that both have the amber Alps keys. This isn't explicitly mentioned in some of the wiki's around the web but it is discussed in some of the forum threads around the web. Posting yet again for anyone who wasn't in the know. You might be able to pluck an A2S4000 for cheaper than an A2S4100 but still get those sweet alps, if that's what you're searching for.
A2S4000 early models - hairpin switches
A2S4000 later models - amber alps
A2S4100 - amber alps
A2S4500 (Apple IIc+) - orange alps