Contextual sidebar and consistency

I am designing a website service for coin collectors and have a question regarding navigation. The control flow is as follows:

  1. User selects country (from map or an alphabetized list).
  2. User selects a time period the beginning of which marks a currency reform (i.e. Germany - Third Reich 1933-1945).
  3. User sees all different types of coins by face value (i.e. if selected country is US, user would see all types of one cent coins (Lincoln Cent, Union shield cent, etc.), then five cent coins and so on). Selects an type.
  4. Sees detailed information about the type and sees a list of all issues (i.e. Lincoln cent: 1941, 1941-S, 1941-D, 1942, ...) with detailed information about each one.

Every page will have a breadcrumb, that shows the path to current page for navigation. I'm also thinking of adding a contextual sidebar to the left, that contains the previous page's items (i.e. if a user is in the detail coin type page, the sidebar would show a list of other types in the same period). Here is a simple visualization of the flow:

enter image description here

Arrows represent hyperlink destinations. Dark rectangles represent contextual sidebars. The shown breadcrumb would appear in the deepest page (coin type).

It would seem to me to be very useful (not needing a full page reload to choose another sibling). But wouldn't this be a bit overwhelming (especially for novice users)? I am also concerned about the consistency. Every sidebar would have its content laid out differently. I know that it's rather abstract at this point. But maybe you have any ideas how to improve on this?

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