Having a (small) knowledge of Sherry,I can tell you a couple of things.
The 1/14 refers to the numbers of butts(large barrels) that this particular Sherry was kept in while maturing (the lower the number, say 1/7) the better the Sherry.
However the fact that your Sherry is numbered at all makes it quite special.
There is no date because there could be some Sherry in your bottle going back 50 years or more,given the production method.
I think this page from Wikipedia bout the Solera method explains it better:~
http://en.wikipedia.org/wiki/Solera
You have a VERY special bottle there,don't give it to anyone who is not likely to appreciate it.
Sherry doesn't mature in the bottle(like wine) but it should be pointed out that Oloroso are the most alcoholic of all Sherries,so just be careful.
Have a look here too:~
http://en.wikipedia.org/wiki/Sherry
I don't think it's worth selling(although quite rare) as they are not unique and don't age like wine.I would drink it,but you may not like Sherry of course?
Sherry can be kept open (but corked) for some time(again unlike wine) but I don't think you will keep it that long once you taste it.
I do envy you your bottle! LOL