Well, it's easy to see it's a model 15, because of the tensioner unit on the faceplate. That is the only model Singer did that way. Value is harder...mostly due to condition issues being very important. If the treadle cabinet is complete and in VERY GOOD to EXCELLENT condition....over $100. If there are condition issues, less, depending on if attachments are there, area of the country, etc. This is actually a very common machine, so don't be fooled by "rare", etc. Hope this helps.