Northants issue the A5 certificates, and have done for some while. They're a PITA TBH. They don't properly fit in the certificate holder I have but they're just that bit too big to fit in a pocket nicely. Any entries have to be made in squinto-vision in order to leave room for more.
Why, oh why can't they just issue all RFD's with a dedicated card reader and make the 'certificate' a plastic credit card type of affair ? All the relevant info could be stored on the card and purchases, sales, and transfers would be instantly added to the polices' own database. This surely would save both the polices' and our time, effort, and paperwork.
The only downside I can see is that non-RFD to non-RFD transfers would require either e-mail or paper notification or mean that both parties had to attend an RFD for 'authentication' and recording of the transfer.