It definitely says "wholesale" - but so many folks - I presume they must have some clients - I have trouble imagining what a "porter" would do there. Perhaps carry all the goods about I guess - as per porters carrying luggage - How does that sound 
Trish
If it's a wholesale draper's, just think about the large rolls of cloth they would have had. In those days, dresses were made by hand by either yourself or a dressmaker, not "ready to wear" as we have these days. So if you were shopping for a dress, coat etc., you would go to the draper's and choose appropriate cloth and have it cut from the roll for you (John Lewis still do this, on rather a smaller scale now!).
The porter would presumably take the cloth deliveries, bring the big rolls to the sales floor, help arrange them on the shelves and also quite possibly be called to help the shop assistant bring a roll down for it to be cut to order.
For really key cloths, where stock was kept, I dare say there would be a "back of house" warehouse, where further supplies would be kept, ready to be moved to the shop floor. Think of the organisation required with such big and heavy merchandise.
And then, I envisage, he might be involved in delivering the cloth parcels to the various customers.
If it really is wholesale, then the "shop" would include customers visiting to purchase rolls of cloth, rather than lengths, and - a bit like carpets - the cloth would need to be cut to the quantity ordered, or the number of rolls required, and then moved to a loading bay for putting on carts for delivery.
I have spent my career in retail - does it show?
