>
> svnadmin dump -r 1:15 sandbox > sandbox-dumpfile
> svnadmin dump -r 18:19 sandbox > sandbox-dumpfile2
>
> Then when it comes time to load, load the first file, then the second

Tried but does not work...

# svnadmin load sandbox-restore < sandbox-dumpfile
The above command restored it up to 15 revision as expected:
<snip>
<<< Started new transaction, based on original revision 15
     * editing path : PartA/trunk/source/README.txt ... done.

------- Committed revision 15 >>>
</snip>

and then the following command:
# svnadmin load sandbox-restore < sandbox-dump2

gave the error message:

<snip>
<<< Started new transaction, based on original revision 18
svnadmin: File already exists: filesystem 'sandbox-restore/db', transaction
'18-a', path 'PartA'
     * adding path : PartA ...
</snip>

The first method also ended up with the same error message.

Any more ideas?

Thanks.