I guess it depends on which version of the classics you have, and if they’re the same… I have two different ones: an older one (right after the kickstarter period) which is glued shut, and a newer one with screws on the back. If you have two of the newer ones, you might try to exchange the interiors.
Be very carefull though: the watch may not be watertight anymore after being opened. You might consider buying a new skin/wrap, p.e. from gadgetwraps. Good luck!