The DWL-610 only has an onboard antenna, and no connector for an external one. It's not problematic for a normal use-case in a laptop, but the metal enclosure of the Soekris blocks everything when it's closed.
An Atheros Mini-PCI card has then been bought to replace in.
To support two wireless NICs, it was enventually decided to buy an extra set of pigtail and antenna and go dirty on the DWL-610 to add an external antenna.
The 5354MP card si based on a Atheros AR5213 chip. It is recognized by OpenBSD as a 5212.
ath0 at pci0 dev 16 function 0 "Atheros AR5212" rev 0x01: irq 11 ath0: AR5213A 5.9 phy 4.3 rf5112a 3.6, FCC2A*, address 00:02:6f:21:ea:79
Unfortunately, it doesn't quit work as a 5212. More specifically, the driver doesn't seem to be able to use 11g modes.
$ ifconfig ath0 media | grep 11g $
In addition, 11b is not very stable and seems to drop until the interface is netstart(8)ed. Indeed, the manpage, as of 4.6, doesn't even mention the AR5213 chip as supported. It may half-work only by chance.
Yet another Mini-PCI card, with a BCM4309 chip (with a sticker saying BCM94309MP) has been found at random. It has been quickly tested as a replacement for the AR5213 card.
The driver doesn't support hostap, though. Tough luck.