HP-28S battery compartment rubber "seal"

[Siegfried]

I acquired a HP-28S and found a mostly loose piece of rubber in the upper battery compartment. It's rectangular about 1x1.2mm in cross-section and several cms long. It seems to emerge from the partitioning between the upper and lower battery compartment about one battery length from the edge of the calculator. When a battery is inserted it is very hard to get it out again due to the friction of the rubber. I had to "knock" the calc on my knee to eventually get it out.

Is this piece of rubber supposed to be there, has it come loose and is supposed to belong elsewhere or might it be a hack to prevent the batteries from banging away the flimsy door?

Thanks for any insights!