Macwester Identification Numbers

[retsina]

I am trying to find what the following identification marking mean which are carved on wood, by the forward "v" bed on my Macwester Wight sloop. (I have also asked the Macwester Assoc chaps) O.N. 339145 R.T. 7 64/100

Many Thanks

 

[mainmarine]

They are the registered number with the MCA and the official tonnage 7 tons and 64/100ths

 

[VicS]

Nothing to do with being a Macwester

Its the Official Number and the Registerd tonnage from a registration on Part 1 of the Register of shipping.

Thats registered tonnage not displacement. It's based on the below decks volume where 100cuft is 1 ton.