rear weight numbers?

I found some rear weights and wonder if Jim or any of our knowledgable readers can help.R28520R second R34810R.These have a larger center and I have seen them on different JD but need to know what they are correct for.The might weigh 100# Thanks

The R2850R will fit the following: 24", 28" P Steel 3010, 28" cast spin-out 3020U
The R34810R will fit the following: 24" cast JD500, 3010 I, 26", 30" cast 4010-4020. Each weighs 115 lbs. May fit more but those are the ones I have for them.

I'll add to what MSD stated that the R34810 weight is listed in all the following parts catalogs.

1256 - 440, 440A and 440B Log Skidders - 29Aug06
4127 - 3030, 3130 Tractors - 12May11 ( FR DE IT ES SV )
4143 - 1830, 2030, 2130 Tractors - 12May11 ( FR DE IT ES SV )
4152 - 1020, 1120 Tractors - 12May11 ( FR DE IT ES SV )
4155 - 1030, 1130, 1630 Tractors - 12May11 ( FR DE IT ES SV )
4164 - 2020, 2120 Tractors (European Edition) - 12May11 ( FR DE IT ES SV )
4173 - 1640, 1840, 2040 Tractors ( -429999) European Edition - 21Jul10 ( FR DE IT ES SV )
4174 - 2040S, 2140 Tractors ( -429999) European Edition - 21Jul10 ( FR DE IT ES SV )
4175 - 3040, 3140 Tractors ( -429999) European Edition - 21Jul10 ( FR DE IT ES SV )
4184 - 1640, 2040, 2040S Tractors (430000- ) - 21Jul10 ( FR DE IT ES SV )
4185 - 2140 Tractor (430000- ) - 21Jul10 ( FR DE IT ES SV )
4186 - 3040, 3140 Tractors (430000- ) - 21Jul10 ( FR DE IT ES SV )
4187 - 2350 and 2550 Tractors (North American Edition) - 16Jul10
4209 - 3050, 3350 Tractors (European Edition) - 25Jun10 ( FR DE IT ES SV )
4210 - 2650, 2650N, 2850 Tractors (Synchro-Transmission)(European Edition) - 01Jul10 ( FR DE IT ES SV )
4211 - 2250, 2450 Tractors (Synchro-Transmission)(European Edition) - 01Jul10 ( FR DE IT ES SV )
4216 - 2355 and 2555 General Purpose Tractors (North American Edition) - 01Jul10
4223 - 2250, 2450, 2650 Tractors (Collar Shift Transmission) (European Edition) - 30Jun10 ( FR DE IT ES SV )

I have the R34810 on my 60 std with 30 inch wheels. The weights were advertised as being for a standard tractor, so I bought them knowing they were not the same as the ones on my 70 std. They fit fine and even have the oval hole. Only an expert would know the difference.

I'd have to check the part number but if they are the ones with the large oval center and a flat outer face- they also work as a "converter" weight to put the 4020 flats on the heavy offset cast of the 4520-4850 wheel.