Re the 2005 manufacturing date: 850 newtons is almost 200 lbs. That's more difficult to measure by hand than an LS landing gear spring or a canopy spring, but it might be advisable to do so. Gas springs don't last forever.

They (and I use that word intentionally) deteriorate on the shelf. The pressure inside the cylinder is still very high even when it's in the extended position. I've seen figures of 1% to 2% loss per annum, which adds up. After they're installed, dust or grit getting into the seal can result in much faster deterioration in force.

When storing a gas spring/strut, hand or position it with the piston rod pointed down. The oil in the cylinder will pool in the bottom of the cylinder and help maintain the seal there. Never store them upside down or laid flat, say, on a workbench or in a toolbox. I learned this the hard way back in my LS-3 landing gear gas strut days when I smugly pulled out the bright, shiny-looking spare I'd carried for several years and was crestfallen to find it was as weak as the one I pulled out of the glider.

This also applies to installation. Given a choice, most of the advice I read is to install in a position where the piston end will be lower than the cylinder end most of the time. It may be (e.g., in my old LS-3, IIRC) that it's positioned one way when the wheel is up but the other way when the wheel is down.

Chip Bearden
JB