Changing the subject, I "swapped" collection websites today with Kevin Booth who has now put his impressive penny collection up onto a website and is happy that I share its URL with Forum members.
it's Kevin's penny collection
Michael Gouby put me in touch with a chap called Frank Hulett who's just had published a new A5-sized booklet devoted to the decimal penny 1971-2020. It's an excellent piece of work with superb illustrations and descriptions of the different varieties that he's come across. He's also discovered that the Brilliant Uncirculated specimens issued by the Royal Mint sometimes have characteristics different from the specimens issued for circulation.
Frank is happy to supply interested collectors with a copy of his splendid book for the cost of postage.
His email address (which he's happy for me to quote) is:
frankhulett@hotmail.com
I recommend it for collectors of decimal coins.
I do have 2 photos of that coin and one does suggest an underlying 7 but the other doesn't. I'm sure it's not there. Trick of the light. Angles and lighting can make such a difference.
Also found in 1856 where PT is large date and OT is small date. I believe that 1858/6 is always small date whereas 1858/3 (or 2), 1858/7 and 1858/? (Bramah 25c) are large date.
1858 small date exists without overdate.