that is the number of the 3d stamps that were sold from this Great Britain 1948 Olympic issue.
There is plenty to read from a google search and you might enjoy reading this site http://www.olympic-museum.de/stamps/stamps1948.htm
I found an auction lot of these, from Norway, asking US $5 for Mint.. that means they are hinged I would expect: that is amazing since the cat value for a mint unhinged set is only £2.25.
Oh well see what value you get from reading me.. you know not to bid dont you 
anyway.. if you want a set mint hinged I do a have a few spare... 1,948th email to tell me the withdrawal date of the stamps will win a mint hinged set... ok .. how about 4th email is that better.
Anyone know the number of stamps issued of the 2 1/2d... should be easy.. I want exact number ok.. if you guess I will give it to whoever is closest.. so that is two sets I will give away...
Must go and rest.. been gardening and sunbathing today.. both garden and me are looking very nice 
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best wishes.. enjoy your stamps..... Michael