stamps101,
I would suspect that the demand for Russian postmarks will rise in the years to come, as has taken place already with Russian stamps. If you have in your hands an extensive collection ("several stockbooks"), possibly arranged and identified by area (within the Russian Empire) or field (for example, railway postmarks), such material would be sought after. Today you can occasionally find some Russian postmarks
ebay items for Russian Offices abroad cancellations, St Petersburg numerical cancellations, etc.
If you do care to show some of your cancellation items here, it would be interesting for everyone and maybe I can offer some additional information.