A Sexual Switching
More art by “Rex” I believe. What’s amusing to me is that his pants are already off, and yet she’s clearly the one who is about to get switched. This tells me his intentions are not only amorous, but also fairly urgent:
Spanking Blog: Adult Erotic Spanking At Its Best
 |  |  |  |  |
The switching is definitely foreplay.
Or maybe he had sex with her before the spanking, or perhaps she came onto him while he was undressing or boinking someone else.
I seem to remember that this appeared in Switch an old British fetish later CP magazine