Nice collection! I saw that modded one (rto) on the bay a while back.
So Eagle actually made 4 different BPP models, with a few variations, changes, and upgrades over the years.
In no particular order:
First is the standard BPP. The one uncle E designed. The original ones all had draw string closures, no slots behind all the pouches, only the two side, and the waist belt was slightly higher, maybe 1 1/2 to 2 inches, than later models, and had a Velcro fold over flap to hold belt in place. Also, did not have hole in lid for camel back. Later versions moved the waist belt down and then had a single padded closed flap to run the belt through. Slots were also added behind all pockets, therefore the side pouches have two slots each. The original pocket in lid flap was Velcro then later became a zipper right inside of pouch. Also, the later packs all had a main roll down flap with a buckle closure instead of the large drawstring.
Specs: ( I think my calculations are correct?)
Standard version
Main compartment: 10" x 18.5" x 6" = 1,110 cu in
Cap pouches: 2.75" x 8" x 2" = 44 cu in
Front pouches: 4.75" x 8" x 3" = 114 cu in
Side pouches: 5.5" x 9" x 2.75" = 136 cu in
total= 1,540 cu in 25.23 liter
Next up in size but not timeline is the MOLLE version. It actually came last I believe. It is just the standard updated BPP with roll down main compartment, etc.. just minus all the exterior pouches, which were replaced with webbing. Main compartment and specs are the same.
Next in size is the RTO.
Side note, the RTO you have is not the original one. Yours looks to be heavily modded, hence all the added stuff. I think the one you have may be able to accept an ALICE frame too, not positive. It actually is not the RTO Patrol pack but based off the Large version. Not really sure what's going on there but it's the only one I've seen, so it's a cool score for sure!
The RTO was in fact made for radio operators and does have extra internal pocket for radio and has two antenna, etc. flaps on top. It's called the Ranger version. This version is actually all the same specs as the original except it is wider and the two front main body pouches are larger. The height and depth are the same as the standard, but the width is the same as the large version.
Specs:
Ranger version
Main compartment: 13.5" x 18.5" x 6" = 1,498 cu in
Cap pouches: 2.75" x 8" x 2" = 44 cu in
Front pouches: 6.25" x 8" x 3" = 150 cu in
Side pouches: 5.5" x 9" x 2.75" = 136 cu in
Slip pocket: 12" x 9" (30.5 cm x 22.75 cm
total= 2,158 cu in 35.36 liter
Last is the large version. It is significantly larger than the standard version and the ranger version.
Specs:
Large version
Main compartment: 13.5" x 22.5" x 8" = 2,430 cu in
Cap pouches: 2.75" x 8" x 2" = 44 cu in
Front pouches: 6.25" x 8" x 3" = 150cu in
Side pouches: 5.5" x 9" x 2.75" = 136 cu in
total= 3,090 cu in 50.63 liter
Hope that helps explain some of the differences. There are quite a few I have seen that are one offs or have been heavily modded
I do own 6 of these in all different configurations, colors, and years and my favorite is the standard version made in the earlyish 2000's. Has all the upgrades and is just more comfortable to me. The MOLLE version is great too for EDC when you don't need all the pockets or just want to add your own gear. I have been trying to get my hands on the RTO for a while now since the little extra width would be nice. More rare than the others for sure, but do pop up from time to time!
-Dex-
I like many have missed your talents here on the Becker forum. 