BY Cam, V1500 Cyg, CD Ind, V1432 Aql, and IGR J19552+0044 are (candidate) asynchronous polars. Although the spin and orbital periods are different in these systems, the differences are small (of order 1% or less), and they are thought to be in a state of temporary asynchronism. Therefore, I will treat them differently from IPs, in which the spin periods are generally thought to be near the equilibrium values.
1RXS J052430.2+424449, nicknamed "Paloma" is a case in between asynchronous polars and normal IPs. I'm now inclined to consider this a low-luminosity, diskless IP, since its synchornization timescale is very long. 1RXS J083842.1-282723 appears to be a case similar to Paloma. If we define APs as polars temporarily dislodged from synchronous rotation, this should be considered an IP.
There is no doubt V471 Tau is a binary consisting of a red dwarf and a white dwarf, and the latter is undoubtedly asynchronously rotating and magnetic. However, accretion appears to be sporadic, at an extremely low level, or both. I prefer to define IPs such that only systems in which accretion usually provides a measurable fraction of the luminosity are included.
Recently, Wilson et al. (2021, MNRAS, 508, 561) announced that CC Cet is a pre-IP.
Again, there is no doubt this is a binary consisting of an M dwarf and an asynchronously rotating magnetic white dwarf. However, so far, there is no indication that accretion currently plays any role in this system, with all non-stellar radiation being attributed to a pulsar-like mechanism and is rotation-powered. While there is a strong similarity to IPs, particularly AE Aqr, it's probably best not to include this among IPs, unless a non-negligible fraction of its luminosity turns out to be accretion powered.
The coherent 25 min period found in this system appears convincing (although we could always use confirmation). I do not include this system because it is an symbiotic star with an M giant mass donor.
Please send your comments, suggestions etc. to Koji.Mukai@nasa.gov and/or Koji.Mukai@umbc.edu