St. Lucia Scott# 159 And 157 / Sg174 And 172 With Mystery Rectangular Cancel

Hi,
I found these 2 St. Lucia Queen Elizabeth II-era stamps together in an old album. They have portions of a boxed cancel, and appear to fit together like they were use on the same cover. I've looked online and in articles, but was unable to see any reference to this boxed cancellation.

Would anyone have any insight on it?

It looks like BAR.......K D.C.O. over what is probably ST. LUCIA, but I couldn't find anything like that, so I was curious. I see that the villages BARBONNEAU and BEXON exist, but those don't fit right.
Thanks!

Maybe Barclay's Bank?

Agree,
Barclays Bank (Dominion, Colonial and Overseas)—Barclays DCO.

Depression to Decolonization: Barclays Bank (DCO) in the West Indies, 1926-1962
Campbell, Carl.#8201;
The Journal of Caribbean History; Kingston Vol. 45, Iss. 2, (2011): 248-VIII.
https://www.proquest.com/docview/928575461

Wow! Very impressive. I would not have came up with that, but it definitely make sense.

So does it mean that this is a revenue usage of the stamps then?

Yes, a revenue/fiscal usage, even though it looks like black ink and not the usual blue/purple/violet was used here.