Cinderella Or Missprint? Where Is It From?

I also posted this in the Cinderella forum but figured it may get more views, increasing the chance of recognition.
Hi Folks.
Anybody have an idea where it is from? Interesting I think is what I believe to be a mistake. Written is P.S. Sirius, when I am pretty sure it should read S.S. Sirius. I know the story of the ship and the race. I just wish I could place the stamp. I also include a close up of some numbers found on the bottom of the stamp ( if that it what I call it) that might be of help (not to me)
Thanks in advance for any help

It appears it was issued (with another matching brown stamp) in the United Kingdom. Here is a link to a pair on ebay
http://www.ebay.com/itm/UK-Vignette...141884196735
Don

Thanks very much Don, could not find any info myself :)