Jon, those are certainly valid stamps, worth 88p and 97p. Various odd values are issued when they are the rates for particular services, such as a worldwide postcard, or a 10g letter to International Zone B. I have in front of me a 2010 presentation pack of stamps celebrating the centenary of Girlguiding in the UK, and their values are 1st (valid indefinitely for the lowest weight step of a 1st Class letter, however much that goes up), 56p, 81p, and 90p (each still worth that number of pence).

Duffield1, you don't have to resell those 1st Class stamps to make a profit, only use them from the next day on! If you bought one on 28 March 2016 and used it any time from 29 March on, you would have made 2p profit, or 3.22%. Even if you took a year to use it, 3.22% p.a. is better than you would have got for your money in a bank account! When, a few years ago, 1st and 2nd Class rates went up 11% and 13% respectively (though it may have been the other way round), I bought enough stamps for my Christmas cards before the rise and so made that profit after about 9 months, equivalent to about 15% and 17% p.a.!

Thays all great but I've stamps which just say 88 and 97 with no pence sign is this the year? If so what is this worth in postal terms?

Would this make stamps a good investment product, then?  So, if I buy £100 of first class stamps on the day before there is a 5p increase in the cost, I'll have 'made' 5p per stamp?

Thank you Owen for your highly informed answer. But how come you are still only a guest? Get yourself in here! Sharpish!

I'll even come up with more stamp questions if that is your speciality. Here's one for you (or for anybody else just as knowledgeable as Owen)....it's a question about the stamp you can see in the picture at the very end of this question. Take a look.

When I was avid stamp collector about 11 or 12 years old I had a mint condition Victorian One Shilling money order with (I believe) a pretty rare history and value...The shilling was in the form of 12 Victorian penny stamps stuck on to the money order.

It was for money paid to a lunatic asylum inmate as assistance money on his release from the infamous Banstead Lunatic Asylum in the 1880s. Nicely printed form too...all attractive copperplate graphics etc, typically Victorian. 

But even more interesting was this...this money order was never cashed in...and the twelve penny stamps were totally unfranked, in pristine mint condition (except for being gummed down to the original printed inmate's release form from Banstead looney bin).

Adding probably more value today to collectors, the shilling's worth of penny stamps were made up of a block of six and three more blocks of two, total 12 pence which was the one shilling for subsistence and/or travel assistance money that ex-inmates were given to help them in their early days of gaining their freedom.

I have never seen one of these before or since so it was probably unique as all the other 'release money' money orders from Banstead would almost certainly have been cashed in. Why this one wasn't I do not know.

Now for the really terrible news! Although I got this antique little bit of philatelic history for free (it was in some old books I'd bought in a junk shop for less than 3p in today's decimal dosh), being in a book had preserved it's 'fresh-as-the-day-it-was-issued' quality. Like it was just printed yesterday.

Like a total idiot, I swapped this sheet of stamps for a little plastic toy submarine you could play with in the bath!

(It had a tube with a bulb on the end you could squeeze to make it sink and surface which made it a real state-of-art toy back then...a fair swap for this bit of philatelic history or so I thought at the time.)

How much would those blocks of stamps be worth today? Remember...a block of six, three blocks of two...pristine unfranked condition...on a probably unique Banstead Lunatic Asylum inmate release form...date early 1880s (can't remember the exact date or the inmates name).

I reckon the plastic submarine would be worth about 50p now if my mum hadn't chucked it away when I grew out of playing 'Run Silent Run Deep' in the bath.

How much do you reckon my stupidity has cost me? Should I cry?

This would have been an Inverted Jenny, only 100 existed, and sticking a 1985 postmark on it surely doesn't make it that special.

Still, perhaps the point of the skit in the film was to show him getting value from what he bought in that the stamp was used to post a postcard - after all, you never ask for the franked stamps you have used to be returned to the sender, you just chuck them away.

Not sure what the rules are regarding currency (or royalty) conversion from shillings (or Goerges) to modern pennies (Lizzy), but I do recall a scene in Brewster's Millions where he buys one of those rare stamps with an upside-down bi-plane on it. The bankers hoping he'd fail in the task of spending $30million in 30 days rejoice at his investing in something (which will mean he fails the task and thus not inherit a much larger amount of cash) but then they receive a postcard with it on (now franked, and value well and truly destroyed).

The simple answer is "yes", and that's from a Royal Mail spokesman a year ago:
http://www.thisismoney.co.uk/money/experts/article-1721593/Can-I-still-use-old-value-postage-stamps.html
If they said "1st" or "2nd" on them, you would not need to add more postage, however as they have a monetary value on them he must combine them to raise the stamped cost of the letter being sent to the appropriate amount.
I have no idea whether you can use an old "1st" stamp, the small sized ones, to post a letter in a larger category though.