Regulation: how good & how much?

[Robe]

Hello all,

Recently my GMT MasterII (16710, Blk/Red) fell from my bed mattress to the floor boards. I could tell this was not going to be good so I monitored it's accuracy.

Prior to the fall it consistently averaged -0.25sec/day/day (measured over numerous 30-31 day periods). It was better by around 10secs than two of my quartz movement watches and matched (in the opposite direction) a Ronda quartz movement watch I have.

Now it is gaining approximately 1sec/day/day (although I have only been able to measure it over 5 days). I always thought that +1 was excellent for a mechanical watch, but after being used to my 16710 running at -0.25 I'm in mourning.

I've tried laying it on its vertical side with winding crown uppermost, however this doesn't seem to slow it down.

I have read informative posts on the forum about regulation, but what I would like to know is:

1. What would be the probability of a Rolex Service Centre returning the same accuracy, +/-0.25 (preferably in the plus zone) before the fall?;

2. I've never had a watch regulated before; how much would this cost?

As an aside I always am concerned about sending my watches for service as I worry about how they will be looked after by the service centre.

Your advice is much appreciated.

Although I haven't posted much I appreciate the excellent work done by many people on this forum.

Regards,

Rob.