A handy transcription did you say it was on this site? I haven't used this site before so still finding its treasures. The mag room sorry was the lovely (not) iPad spell checker it was just supposed to say "the groom" lol. The person that did the transcription seems to have some inside knowledge as there's nothing on the cert that says that Thomas Hulin is the parish clerk. There again other than the "Boten" Thomas is the only other illegible bit it looks more like Marcus, I wouldn't have guessed Thomas. The "Boten" of Yorkley is written next to the groom & Ha (a superscript underlined) of St Briavels is written next to the Bride. It's a certified facsimile that I have from the GRO, who also guessed Boten. If you squint you can imagine it says "both" so given the transcribers other knowledge I'm going to go with that. On the census the following year, they are living with the brides family, although the address is listed as Middle Forge, Tintern Parva, not St Briavels. I am still to track down Samuel Jones, until very recently the family doing research before me had him down as John not Samuel. I know one of the families goes from here to Ireland from pass down from my great grandmother their granddaughter. I have some jewellery of Ruth's mothers, at least I thought it was Ruth's mothers as my mothers little made up rhyme that counted back daughter to mother after Brown came Smith but I think Ruth's mother was Bailey so perhaps it's Edwards mother whose Smith. The jewellery was made in Ireland. So I've got a long way to go yet but perseverance brings rewards.
Many Thanks for your help
Lisa

Have you seen this site's transcript of the Marriage PR ?, namely

Record_ID: 23093
Entry_Number: 84
Year: 1840
Month: Oct
Day: 25
Grooms_Surname: JONES
Grooms_Forenames: Edward
Grooms_Age: Full
Groom_Condition: Bachelor
Grooms_Occupation: Engaged in iron work
Grooms_Residence: Both of Yorkley H[undre]d of St Briavels
Grooms_Fathers_Surname: Jones
Grooms_Fathers_Forenames: Samuel
Grooms_Fathers_Occupation: Engaged in iron work
Brides_Surname: BROWN
Brides_Forenames: Ruth
Brides_Age: Full
Brides_Condition: Spinster
Brides_Occupation:
Brides_Residence:
Brides_Fathers_Surname: Brown
Brides_Fathers_Forenames: James
Brides_Fathers_Occupation: Engaged in iron works
Licence_or_Banns: Banns
Date_of_Banns:
Signature_or_Mark: Both mark
Witness_1: Thomas Hulin-P Clerk
Witness_2: Emma Hulin
Other_Witnesses:
Officiating_Minister: [illegible]
Event: Marriage
Memoranda:
Notes:
Register_Reference: P278 IN 1/12
Page_Number: 42
Parish_Chapel: St Briavels
Soundex_Groom: J520
Soundex_Bride: B650

I wonder if "Boten" is an erroneous transcription of the old handwritten "Both of" of St Briavels, as more accurately transcribed above ?

I don't know for sure, but I presume the Certificate you have is transcribed from the same original PR as this ?.

It may be possible for one of this site's volunteers to take another look at the original PR. I once had a similar enquiry and they kindly checked the PR at Gloster Archives, and even sent me a photo of it, for which I was vey gratefull. See http://www.forest-of-dean.net/index.php/resources/parish-records

If you've not done so I recommend reading this detailed history of Yorkley life
http://www.british-history.ac.uk/search.aspx?query=yorkley

Finally, sorry for asking, but what do you mean by "mag room" ?.

Hope this helps, Jeff.