This is an all-too-common way to advertise a Herald for sale. It is also, intentional or unintentional, a FALSE way to advertise a Herald for sale.
There are, of course, genuine Herald convertibles. These cars, if original, will have a suffix in the commission number of either "LCV" or "CV"; the "L" denotes left-hand drive, but there is no code for right-hand drive.
The vast majority of Heralds built, however, were saloons (sedans as we Americans call them). These will have a suffix of "[L]DL" or possibly "..DLRS"; the latter "RS" refers to a car built at the factory with a "sunshine" roof.
Where the confusion comes in is that this roof (and the similar roof on the fairly rare coupé model up to 1964) can be removed from the car with just a few bolts undone! Many, many people do just this to enjoy open-air motoring, but it really is not recommended to do this for any length of time. When I see an advertisement such as the one you mention, I always suspect that the car is really a saloon and that the roof is either in another part of the seller's garage or is lost completely. /ubbthreads/images/graemlins/frown.gif
As for possible value, I really cannot say from my own perspective here in the United States. You might want to try contacting the Triumph Sports Six Club Denmark:
Jens Conrad
Parkvaenget 6
8600
Silkeborg
Denmark
I cannot find a web address for them, but there are other Triumph clubs in nearby countries such as Norway: <
https://www.norsktriumphklubb.no/>. And there is a worldwide e-mail list dedicated to Triumph Heralds (but I don't know if Forum rules allow me to mention it; contact me privately for more information).