Before I go on though, a small introduction is necessary. Maulana Qasim Nanotwi was the founder of Dar-ul-Uloom Deoband, a seminary in the city of the same name, Deoband, India. This institute flowered into one of the most prolific centres of Islamic learning and produced great towers of knowledge who spread to all parts of the Sub-continent and served the Deen to their utmost.
Today, many Ulema that hail from the sub-continent are affiliated with the seminary in some way or another through their teachers, and there are many luminaries of this school present in Western countries as well. http://www.www.darululoom-deoband.com/.
To read more about Maulana Qasim visit http://darululoom-deoband.com/english/index.htm and click on Introduction of ulema-e-Deoband and then choose 'The six great ones (Founders)'
Now back to the topic, the booklet that was published in defense of the Ulema of Deoband is called Al-Muhannad alal Mufannad and I will translate the section on Maulana Qasim for your benefit. I have also added my own comments in square brackets to aid understanding.
16th Question : Do you accept that there may be another prophet after Prophet Muhammad (peace be upon him) even though he is the Seal of the prophets and his declaration that 'there will be no prophet after me' has reached an uncontestable degree ( wa qad tawatur ma'nan) and upon this the whole ummah is unanimous(ijma). What is your opinion about the person whom, after this, believes that there could be a Prophet after Muhammad (peace be upon him)? And has anyone among you or your teachers said anything of this kind?
Answer: Our belief and that of our teachers is that our Master and Maula, our beloved Intercessor (peace be upon him) is the Seal of the Prophets and there is no prophet after him as Allah has declared in his Book
'وَلَكِن رَّسُولَ اللَّهِ وَخَاتَمَ النَّبِيِّينَ
and this is what is evidenced from the many sayings of the Messenger (upon him be peace) that have reached the degree of uncontestibility, also by the unanimity of the ummah. Impossible it is that any one of us could deny this because any person who rejects this [finality] is an unbeliever and apostate in our opinion because he is denying the clear Proof.
Our Shaikh Maulana Qasim Nanotwi has, through his astuteness, actually outlined it in a profound way and given his Finality more perfectness and made it more decisive.
Whatever he said in his treatise 'Tahdheer un Naas', its summary is that Finality (khatamiyah) is a trait that is of two types. The first being Finality of era and that is that RasoolAllah (peace be upon him) is the Seal and the Final of the prophets because he came in the last period, after all the others. So, he is a Seal in the sense that he 'sealed' the line of prophets and came last.
The second type is Finality in itself, meaning that it is his Prophethood that the prophethood of others fall under and finish at.
Muhammad rasoolAllah (peace be upon him) is both the Seal with regards to his position in time, and the Seal in essence. He is the most Perfect and unequaled [among the prophets] and the centre of the circle of Prophethood.
He is not the Seal of Prophethood only in the sense of coming in the last era, because it is not something that constitutes much excellence in itself [for example Yaqoob and Yahya (peace be upon them) came after, in time, to Ibrahim (peace be upon him) but the latter holds a higher rank] but actually Muhammad rasoolAllah's (peace be upon him) greatness and mastership, and the pinnacle of perfection and honour will come from being the Seal in both the senses, timewise and finality in itself [where all other merits converge and finish at].
Merely saying Muhammad RasoolAllah (peace be upon him) is the last of the prophets timewise will not raise his ranks to the highest degree and mastery nor will it do justice to his complete nobility and augustness.
This erudite exposition is actually the product of Maulana's insight. We don't think anyone of the preceding ulema and deep-thinking scholars have been able to approach such a field and it has instead become a reason of, in the opinion of the Innovators of Hindustan, disbelief and misguidance.
These innovators have misled their followers and alleged that this is actually a rejection of the finality of the holy Prophet (peace be upon him). Oh how deplorable! I swear on my life that this is nothing but deceipt of the highest order and slander, borne out of hatred and grudge with the Friends of Allah and Allah's Way (sunnat-ul-Allah) has been like this with his Prophets and Friends.