The site marked with the ? is an SA-2 site. The shadow of the launcher might make it appear to be a two armed launcher but it is, indeed, a single-rail SA-2.

When viewed from overhead, the two-rail SA-3 launcher resembles a grasshopper whilst the four-rail version looks like a stubby dinner fork.

The northernmost of the two sites is an SA-3 site. You can clearly see the twin-arm launchers and you can even see a missile transporter backed up to the launcher in the 4 o'clock position, in the process of moving missiles either on to or off of the launcher.