This week's poem, "Coram's Cloth", is by Tony Curtis and comes from an anthology he has recently edited for Seren Books called Tokens for the Foundlings. Packed with a variety of mainly contemporary poems about children and childhood, the collection is published for the benefit of the Foundling Museum in Bloomsbury. The Foundling hospital itself, established in 1739 by Thomas Coram, no longer stands, but its good work continues via the charity Coram.

The project, Curtis explains, came about through the imaginative connection he had made with the work of the textile artist Rozanne Hawksley. "Coram's Cloth", first published as a broadsheet by Mulfran Press, reflects the hospital's practice of retaining tokens for the purpose of identification should the parent return later to reclaim the child. The token that the poem's narrator has left with the orphanage is a piece of fabric cut from her dress. Tokens included more valuable items like lockets or rings, so the humble nature of this one tells us something about the unfortunate woman's circumstances. The poem's focus, though, is not on the token itself, but the hole left by the cut-out scrap of fabric.

The similarity of sound between "token" and "taken" is significant, and these words form the "B" rhyme in stanza one. The mother's loss, centred on the image of a space which she cannot forget or leave alone, is immediately palpable: "This hole in my dress that I worry and enlarge / with fingering …"

The woman's diction is affectingly complex. Now we hear the informal tones of a working-class dialect ("them at the Foundlings", "my precious") and now the effort to constrain emotion and demonstrate obedience by echoing the voice of officialdom.

The opening lines of the second stanza combine both registers: "Whereby that cloth shall be the means, / they say, for me to recognise myself to her". The speaker begins formally, then muddles her grammar under pressure of anticipated emotion in "to recognise myself to her". This strange construction is all the more effective in underlining a psychological truth. The hole in the dress is no less a hole in the woman's identity. She will know herself again only when she recognises herself in (and is recognised by?) her child.

The formal register is recovered in the next two lines, abstractions evoking the distance in status between the mother and the organisation. There is some hint of magic, perhaps, in the idea of "the world's workings and men's schemes" turning "to mine and her favour". Again, in the grammatical slip of "mine" we feel the thrust of emotion, the tightening of the bond. "Mine" is more declarative than "my" and carries a greater possessive weight in the very sound.

The sentence might have continued into the next stanza, but a full stop intervenes, and so gives the subordinate clause a sharper framing: "Though the nights grow frost / and my fortunes tip." In the unexpected phrase, substituting a noun for the more usual adjective, frosty, and making "grow" into a transitive verb, the frost becomes organic, almost hair-like: we can feel how icily it prickles the skin. It reminds us that the woman has perhaps only this one dress, a thin dress, a dress with the tattering hole. The word "tip" suggests a sudden, vicious movement which seems to take the woman with it.

She hasn't given up hope, but, as she obsessively touches the edges of the hole, her fear – that the hole will be too big, the token too small – encapsulates her sense of an ever-widening gap between herself and her child. It's an anxiety that encodes the power of those she deems in control versus her own helplessness. It may imply that she is nearing a mental tipping point. There must be so much for her to worry about, but what troubles her most is the matching of the hole in her dress to the fabric token. By the harsh logic her life has taught her, if the fit is deemed wrong by those in authority, she will lose the child – and, with horrible irony, all through her own helpless "worrying" at the hole.

The economy of the monologue is part of its appeal. It would be easy to say too much, or press the symbolism too hard. The poet resists such temptations. His device is to stand back and let the woman seem to present her own thoughts, giving her a voice of such pained candour and humility we can almost hear it. Technically, through its varying degrees of rhyme, the poem plays deftly with notions of fitting and not fitting. "Frost" does not find a strong chime in "fit". "Space" has a closer rhyme, but not a perfect one, in the poem's perfectly placed last word. That sibilant pararhyme seems filled with sighs, expressing the desire for things to come right – for mother and child, fabric and hole, to fit somehow together again. The tender hope is freighted with uncertainty, the doubt offset by the solidity of a name which suddenly becomes a presence: "Alice".

Coram's Cloth

This hole cut in my dress that I worry and enlarge
with fingering is where the piece was taken
by them at the Foundlings as token
when I left my precious in their charge.

Whereby that cloth shall be the means,
they say, for me to recognise myself to her
when the world's workings and men's schemes
shall turn to mine and her favour.

Though the nights grow frost
and my fortunes tip. By then, I fear, the space
of my worrying will surely not fit
to the piece they kept, and wrote beside Alice.