Ordinarily, I might recommend that you perform a bulk transfer of the 200 assets to the company where you want them.  However, this procedure will not do exactly what you are asking. 

Let me explain what will happen.  As a result of the transfer, new assets will be created in the company to which you transfer the assets.  The old assets will remain in the old company but in the transferred state, i.e., they will no longer depreciate.  However, the acquisition value on the new assets after the transfer will reflect the same value as was recorded on the old assets.  In fact, all of the critical fields will remain the same.  But the beginning fields will be filled in.  The program will automatically fill the values into the beginning fields, capturing the depreciation on the assets as of the month prior to your transfer date. 

Any remaining depreciation on the asset, which would be the equivalent of your NBV on the assets, will depreciate in the new company.  Thus, the resulting effect will accomplish your objectives, as it appears to me, but the new asset records will not reflect acquisition values equivalent to net book values which seems to be important to you in this process.

So, what could you do in order to create new asset records with acquisition values equivalent to the net book values?  Here are some steps you could follow:

1. Create a group of assets for the 200 you want to sell to your other company.
2. Perform a custom export on this group, selecting all of the fields that you will want to capture onto your new asset records. Be sure to include the NBV.
3. Be aware that the custom export only works for one book at a time. It’s clear from your post that you want to pull information from the Internal book, but you will need to go through this iteration for each book you need to keep in your new company.  This means that if you are keeping multiple books, you will need to create a master spreadsheet using copy and paste from the other spreadsheets you create via the custom export.
4. Use the master spreadsheet to create the 200 new assets in their destination company by performing a custom import. In this process, you will map the NBV to the acquisition value in the Internal book.
5. Perform a bulk disposal on the group of 200 assets in the old company.

As you may infer from these steps, this process can be complicated.  You might consider contacting the Professional Services Group through your Sage account rep.  A consultant from that team can perform this service for you for a negotiated fee.  And maybe, that might be faster than trying to do it yourself, especially if you're not familiar with some of the steps I've delineated.

Thank you, Bob!

Appreciate the insights and thorough answer.

You're welcome!

;=)