Value of mint condition first pressing of Sgt. Pepper?

OK:  I have checked all the markings on the record and jacket.

I will check all the resources the helpful responses have indicated, but here's the info I have:

It is made in Great Britain in 1967PCS 7027On the label it says YEX 637, but on the vinyl, 636.5.  The letters HTM are (what looks to be) etched on the inner circle of the vinyl.
I have only played this a few times; it looks like brand new and plays beautifully.

Any ideas?

The things you mention don’t mean anything in answering the question if it’s a first pressing. ’Made in Great Britain’, the publishing date 1967, the catalogue number PCS 7027 and the tape number YEX 637 (side 1) and 638 (side 2) are mentioned on just about every UK pressing. If the label is the Black/yellow parlophone label and it includes the text ’sold in UK, subject to resale price conditions, see price list’, than chances are you have a first pressing.

But the really important info is in the run out grooves. First pressings need to have the first matrix, which reads as YEX 637 -1 and YEX 638 -1 at 6 o’clock. Than it needs to have a first mother, to be read as ’1’ at 9 o’clock. Finally you need to check the stamper number at 3 o’clock, which uses the letters GRAMOPHLTD (G being first stamper, etc.). The earlier the better. Beatles records sold by the truck loads, so stampers codes with two or even three letters (e.g GAP = 136th stamper) are very common. If you have one letter stampers on both sides you have a very early first pressing.

First stereo pressings in mint condition are less valuable than mono, but still in the hunderds. However, you mention the letters HTM. These are mostly seen on EMI pressings of the mid 70’s, so if present it’s unlikely to be a first pressing.

Now THAT was an explanation, Edgewear! I purchased a 1st issue UK Sgt Pepper today and was all excited and congratulating myself. Then I read your post and noticed my copy has what looks like a GBP in the runout (along with a YEX 637-1 matrix). So although its a first issue its not a VERY early pressing. Still happy to have it though!