The 1720's are good machines, I think all the XX 20 seies Fords were. I have to agree though, price seems high especially for an 88 model. I would guess it has a pin on bucket. In my area, you can pick up a FWD 1920 w/loader for that price, which I have always felt are very good machines. The 1920 has a little more weight, 5 more HP, 4 cylinder engine and slightly larger tires. I have a coworker currently selling his 1000 hour 1999 model 1925 w/loader asking something in the $9K range. Here are the serial numbers for the 1720's if there is a question about the exact year.
1987: UL21001
1988: UL22701
1989: UL26556
1990: UL28601
1991: UL30784
1992: UL32230
1993: UL33920
1994: UL35013
1995: UL36435
1996: UL37607
1997: UL38466
1998: UL40069
1999: UL41414