Ciao there Simon! Hows it going all these while?! Trust everything is well over there in England. Wells, thanks to your help last time, I now own a 249 as well^^ Thus I can help you in your question.
Simply, the 249 does NOT have a stop- seconds function. That is, when you pull out the crown, no lever or such rests on the balance of the watch, therefore the watch keeps on running whether the crown is pulled out or not.
The best way to set the 249 ( as i have discovered, knowing me and me being ULTRA-ANAL about precise time setting to a standard e.g. atomic time) is to move the minute hand such that it is about halfway between minutes, and when it is about 10 seconds or less, ( best is around 10 ~ 8 seconds) before the next minute that is about to come, you move the minute hand over the index of the next minute as accurately as your eye can set, then push in the crown while looking at the time standard when it reaches 00 seconds. So e.g. the next time that is coming up is say 13:07:00 , you put the minute hands at 13:06:30 ( there abouts, so halfway between "06 & "07) and at 13:06:50 on your atomic time standard ( hopefully it is digital like the table clock i have here which is radio- adjusted to the atomic time of Japan) you put the minutes hand DIRECTLY over the 13:07:00 index on the "railway" around the dial of the 249. Then when 13:07:00 comes, it should be time to push in the crown, so you push it in with one mighty push STRAIGHT into the horizontal so as not to knock the minute hand off course by one bit. Voila, you got your PAM 249 set to at least within 2 sec for at least the 1st day, we all know that by the 2nd day, it will definitely NOT be on the dot no matter what you did the previous day, it houses an ETA, what more can I say? ( My heart aches at this)
I hope this helps my friend, and keep it cool with your 249 always!
Ciao ciao