Does anyone know when the ink windows in the Aurora 88s changed colors? I have an 88 #994559 with an amber looking window, and another, #1149369 with reddish tint. I also note that the cap on the older model is slightly shorter than on the newer one. Does anyone have info on that. Also I just acquired an vintage 88 Nikargenta. Does this cap require any special treatment other than the usual care? Thanks for any light you can shed on these questions as I try to learn more than I've already gleaned from this forum about these great pens.