I would say 47th week of 99, I would though expect the arrow head after the nine, ie 479> or 479⇦br/>
one arrow denotes 80's and the other 90's but not sure which is which now.
In 2000 the date became 4 digits and clear to read, first two the week and second pair the year, therefore your tyres are still 10yrs old and well passed their useful life