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So with this here, we have the info 'From Holland, 1696. Guards move as rooks, capture as bishops. Ensigns move as bishops, capture as rooks.' This page here .. http://www.quadibloc.com/chess/ch0502.htm

it says here .. 'D. B. Pritchard's Encyclopedia of Chess Variants brought to my attention an extended form of Chess from 1696, called Enlarged and Improved Chess.' (And further down the page, we have) ... 'the two added pieces were the Ensign, a Bishop-mover/Rook-capturer, and the Guard, a Rook-mover/Bishop-capturer.'

So, these two pieces sound exactly like the ones in this game yeah, https://www.chessvariants.com/diffmove.dir/thinktank.html

The Bisroo - Bishop-mover/Rook-capturer

The Roobis - Rook-mover/Bishop-capturer

that is correct yes, hopefully i got it right lol

V.R.Parton also was interested in these divergent pieces. He used the "Biok" (mBcR) and the "Roshop" (mRcB) in his Half-Queen's chess. The Biok is a name that was invented by Lewis Carroll. Parton also proposed a Quight (mQcN) and a Kneen (mNcQ).

The Enlarger and Improved Chess is also described in my book A World Of Chess. It seems to have appeared in Dutch edition of a treatise by Greco circa 1696. Interestingly, modern Chess had barely two hundred years only, so this game is one of the earliest variants of modern chess.

Yes, i see the names 'Biok' and 'Roshop' and also the 'Quight' and 'Kneen' on the Wiki fairy piece page ..

https://en.wikipedia.org/wiki/Fairy_chess_piece#:~:text=A%20fairy%20chess%20piece%2C%20variant,in%20the%20way%20they%20move.

Sure, I am the one who is making most updates on this page :=)

I did once measure the value of the Kneen and the Quight. This confirmed what I had also observed in divegring short-range leapers: roughly 2/3 of the value of a piece is determined by its captures, 1/3 by its non-captures. The value of the Quight was thus about 5, and that of the Kneen about 7 Pawns, in a FIDE context.

I did observe an interesting irregularity, though: testing divergent compounds of Knight and Commoner, which themselves test as nearly equal in value, the combination mNcK (Kning?) proved to be about half a Pawn stronger than the other combinations. I suspect that there are some penalties and bonuses on the move pattern as a whole, which happen to cancel each other, so that its value is in the end not much different from that of other 8-target leapers. The K move set is very poor on 'speed', but very good on 'concentration' (i.e. lots of orthogonal contacts between the target squares). Speed seems to be mainly important on non-captures, determining how many turns you will need to reach the location where you are needed (such as a promotion square). Concentration seems to be mainly important for captures, determining whether you can attack Pawns in such a way that they cannot simply move away, and whether the piece has mating potential. The Kning thus has the best of both worlds: the Knight move provides the speed, and the King captures the concentration.

Excellent post, thank you for this analysis. What is value of the Kning in FIDE contest? (You said 1/2 Pawn more than other combinations, which ones? The Kight?)

Commoner, Knight and Kight all tested as equally valuable, from an opening position. (E.g. when I replaced the Knights of one player by Commoners it did not affect the win rates.)

When you can read German in Fraktur printing, this digitised book shows the variant under the title "Vom vermehrten und vergrößerten Schachspiele, genannt das Spanische":

https://books.google.de/books?id=dv1dAAAAcAAJ&pg=PA44&lpg=PA44&dq=%22Bickelheringe%22&source=bl&ots=KlPjbEnTRs&sig=ACfU3U3_0lJIKKQ5eITSb4KYJPxccK0v7g&hl=en&sa=X&ved=2ahUKEwi7-taS1vTvAhXRgf0HHUEmCxAQ6AEwAXoECAMQAw#v=onepage&q=%22Bickelheringe%22&f=false

It gives interesting German translations of the piece names, the Bishop is a "Bickelhering" (a fool in commedy), the Ensign is a Fähnrich, and the Guard is a Trabant.

good finding Danke schön