abbreviations on birth certificates

[shumagh]

Hi.
I've decided to post this message here because it's such a basic question.
On several certificates in my possession, under the details of where born, there are abbreviations, either R.D. or, I think, R.S.D (can't quite make out the middle letter).
 I've just assumed R.D. stands for rural district, but is this right? If so, what does R.S.D stand for? It's beginning to niggle me that I don't know! Thanks Shumagh

[Necromancer]

Rural District - yes

RSD - maybe Rural Sanitary District, sounds odd ! but I've seen it, also Urban SD   

http://en.wikipedia.org/wiki/Sanitary_district

[shumagh]

 Just had a thought (yeah, sometimes my brain works!) What about registration district and registration sub-district? Is it just that obvious? If so, apologies for time-wasting. Shumagh

[shumagh]

Sorry PastMaster, our posts crossed. Thanks for the info.... now I know!
Shumagh