Rodgcam - you just had to go and mention the Van Dieten auction! - I don't need any more competition

Floortrader - now I'm getting envious - you posted in your last 10 pages some very nice stuff, including a number of items I don't have, which I wish I did.
My comments:
I was not aware of the Japanese approving of the Republicans overprinting their stamps before they surrendered. My references imply that the Japanese surrendered in mid-August and just let the Republicans take over the post office and other civil functions. The Republicans then started overprinting the Dutch and Japanese stamps in stock as many other revolutionary governments have done until they can get up and running. Admittedly, some of their early efforts were crude.
If you have a link to the source that says the Japanese allowed overprinting before they surrendered, I would like you to send it to me.
Page 1 - I think the top stamp, rather than defaced, is a poor attempt at a fake Japanese cross overprint. The one and 2 line overprints were crude early Republican stamps, but the ease of forgery is so great in these, that most purists will only put in their collection such stamps cancelled with a clear revolutionary date between Aug 45 and Dec 49.
On the bottom left you have something very interesting. That appears to be a Scott 2L5 with an error of missing Repoeblik Indonesia. It is a known error - listed in Dai Nippon with a catalogue number of 0105od - value $48 (all values I mention are from 2005 - for anything cataloguing over about $10 you can probably increase it by 50% - or sometimes more (or sometimes less)). I wish I had one of those.
Page 2 - a nice selection of "Rep Indonesia" overprints, both type 211 and 213. These were from Sumatra. The boxed Repoeblik Indonesia stamps below those are type 52 - from Java
Page 3 - Very nice "Rep In-" over "donesia" in a frame type 54 on Konijnenburgs. These are harder to find than such overprints without other overprints as well. That grouping catalogues at about $90.
Page 5 - at the top, the same type 54 frame overprints on Konijnenburgs, but with T overprints as well - that grouping catalogues at about $39 - easier to find than the plain 54s
Right below those is a very nice grouping of "Rep Indonesia" type 211 with T overprints, from 10c to 80c - they cat about $50. I don't have a number of those. the 1 guilder and 2g don't quite fit though - the 2g has a type 54 overprint, and I can't quite tell what's going on on the 1g - it may be a 54 as well
Page 6 - The 2nd 50c stamp is not a REP. IND., but rather a REP: IND:
REP. IND. is a different and very expensive animal.
You have some more very nice ones at the bottom - those are not defaced - they are actual overprints. the crude circles are Sumatra type 13 - here they are combined with a 213 and a 215 it looks like. The crude block on the right looks like a type 14 Sumatra overprint (assuming it's not bigger than 13 x 16mm)- supposedly not rare by catalogue value - but just try and find one! I've been trying for 3-4 years now.
The thing that originally got me interested in this field was the fact that you could have 2,3, and even 4 overprints, and it could still be a MNH stamp.
Page 7 - Upper left - 50sen on 17 1/2c Repoeblik Indonesia. This one drives me nuts. Every small time internet dealer (and auction houses too - I'm talking to you Universal Philatelic!) thinks they have Scott 2L8 cataloging about $100. It says immediately below that the Japanese overprints alter the value. As in the very common T overprint as seen here, which lowers the value to $5.
Page 10 - I agree that it's not clear what's going on in that upper left stamp - I would want a closer look at it. The upper right is a 213v-87v-16b Republican stamp. (a blurry "Rep Indonesia" diagonally)
The 2 lower stamps appear to have Japanese overprints as well - 82z on the left, 87v on the right.
On the whole you've got a great start to a fascinating area here. It is complicated and requires a lot of resources - after 3-4 years of working hard at it, I would say I have intermediate knowledge at best