In a 2014 thread in the Camillus sub-forum titled Remington Knives by Camillus
on page 2 member Vit_213 wrote R4 Utility knives were made 1988-1993. Other than taking a guess that your relative probably bought all 3 not too many years apart I can only say Camillus made the R2 and R8 some time in the roughly 25 years they made Remingtons ending in 2007 when they went out of business.
If you want to sell the R4 I'm interested.
Happy New Year!