Hi Greg
Sorry you're struggling

Worth perservering though - SP is good value for money cert-wise especialy once you've gotten the hang of getting as much as you can out of the free searches first...
Once you have registered, confirmed and logged in - you can definitely freely perform searches in the Stat. Reg. index (not to be confused with the blue "Free Surname Search" box on the Home page).
You dont'need credits to search and be told there is for example 1 person matching your search criteria.
Anyway.....
SEARCH: Peter GEDDES deathsBetween 1901 (when he was seen on the Census)
to 1955 (who's to say he didn't live to be a 100

)
RESULT:38 Peter GEDDES deaths in all Scotland
(MMS is not captured on the Index until 1974, though on actual certs it is there if it was informed))
NOW, progressively narrow the search result:14 of those 38 are in Banffshire
4 of the 14 were born 1853+/-5years in Banffshire (1848 to 1858)
3 of those 4 had their deaths registered specifically in Rathven and all by end of 1939
1 of the 3 died by 1910 - the other 2 died between 1921 and 1939
So - you have 3 Peter GEDDES who died in Rathven between 1901 and 1939, who were born anytime between 1848 and 1858.
When you pay 1 credit to view an index page, your search is saved (you can refer back to it for free). You also get a maximum of 20 listings per page / per credit. The year and age indexed will be on that 1 credit Index result.
So you can search the 14 Peter GEDDES who died in Banffshire, and view the results for 1 credit. Then you can pick out the one(s) you want to buy a cert for (for 5 more credits apiece).
Trouble is - the free search has identified 3 possibilities - and that's only by assuming his death is registered in Rathven btw 1901 & 1939. Once you view the Index page for 1 credit, it may be the 14 entries clearly identify the one most likely to be yours - which in turn may be one of those 3 in Rathven.
Keep in mind, though:
The age and pob as seen on the Census of 1901 (abt 1855 Peterhead, Aberdeenshire, as opposed to:
The age and pob you believe to be correct (abt 1851 Port Gordon), and combine with:
The fact ages on a death record can be mis-taken (mis-informed or not known correctly by informant) and consider:
He may not have died in Rathven (so not registered there), or not even in Banffshire. He may have outlived the wife, moved counties to be with one of the children or died at sea...anything is possible.
Lucky dip, I'm afraid. In a perfect world with pots of dosh, one would try narrow his probable death by first seeing what his wife's cert said, his children's post 1901 marriages if he was stated as deceased.
If you priority is to acertain his parents, I would plump for the 1874 marriage first - major reason being Peter himself would have provided the information thereon. His parents details on his death cert will have been informed by someone else - who may have gotten something wrong!
Cheers
AMBLY