The use of dél in "por los señores dél un libro"

Question

From the Tasa of Don Quixote:

Yo, Juan Gallo de Andrada, escribano de Cámara del Rey nuestro señor, de los que residen en su Consejo, certifico y doy fe que, habiendo visto por los señores dél un libro intitulado El ingenioso hidalgo de la Mancha, compuesto por Miguel de Cervantes Saavedra, tasaron cada pliego del dicho libro a tres maravedís y medio; el cual tiene ochenta y tres pliegos, que al dicho precio monta el dicho libro docientos y noventa maravedís y medio, en que se ha de vender en papel; y dieron licencia para que a este precio se pueda vender, y mandaron que esta tasa se ponga al principio del dicho libro, y no se pueda vender sin ella. Y, para que dello conste, di la presente en Valladolid, a veinte días del mes de deciembre de mil y seiscientos y cuatro años.

I am reading this along the lines of "having seen for the gentlemen a book entitled The ingenious hidalgo of la Mancha," and operating under the assumption that 'the gentlemen' is a deferential way of referring to the members of the aforementioned Consejo. However, the use of dél is giving me pause. At first I was interpreting this as the contracted 'de el' and thought it just must be a feature of the older form of the language that 'de' had a diacritic over it, but that doesn't make any sense to me in the context, and I don't know what else it might be.

Answer 1

'Dél' certainly exists and is equivalent to 'de él' (of him), only that was used long time ago and now it is rare to find.

The official dictionary of Spanish, DLE, still mentions it:

dél

1. contracc. desus. De él.

Where 'contracc. desus.' means 'contracción en desuso' (contraction in disuse).

Checking old dictionaries I see it was first mentioned in 1884 Academia Usual already as in disuse:

Contrac. ant. de la prep. de y el pron. él. De él.

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So going back to the sentence you mention:

habiendo visto por los señores dél un libro intitulado El ingenioso hidalgo de la Mancha

It means something like:

having seen by his masters a book named El ingenioso hidalgo de la Mancha

Answer 2

On second reading I realized I didn't understand the quoted text either, so I looked around for some more help, and found this:

I, Juan Gallo de Andrada, notary of the Chamber of the king our Lord, of whose members I am one, certify and attest that, having seen on behalf of the Lords of this Council a book entitled El ingenioso hidalgo de la Mancha, authored by Miguel de Cervantes Saavedra....

This confirms that the él in the contraction dél refers back to Consejo.

Here's a slightly different version in English, in case it helps:

I, Juan Gallo de Andrada, scribe for the king's Council, certify and attest that, having seen on behalf of its members [the members of it] a book entitled El ingenioso hidalgo de la Mancha, written by Miguel de Cervantes Saavedra....